0001489136-19-000011 | 10-K | XBRL Viewer

Print Document View Excel Document

Document and Entity Information - USD ($)	12 Months Ended
Document and Entity Information - USD ($)	Dec. 31, 2018	Jan. 31, 2019	Jun. 30, 2018
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2018
Document Fiscal Period Focus	FY
Document Fiscal Year Focus	2018
Entity Registrant Name	SEMGROUP CORPORATION
Entity Central Index Key	0001489136
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Well-known Seasoned Issuer	Yes
Entity Public Float			$ 1,990,614,027
Entity Current Reporting Status	No
Entity Voluntary Filers	No
Entity Emerging Growth Company	false
Entity Small Business	false
Entity Shell Company	false
Class A [Member]
Entity Common Stock, Shares Outstanding		79,155,214
Class B
Entity Common Stock, Shares Outstanding		0

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 86,655	$ 93,699
Accounts receivable (net of allowance of $2,244 and $2,628, respectively)	562,214	653,484
Receivable from affiliates	295	1,691
Inventories	49,397	101,665
Current assets held for sale	0	38,063
Other current assets	17,264	14,297
Total current assets	715,825	902,899
Property, plant and equipment (net of accumulated depreciation of $607,903 and $444,842, respectively)	3,457,326	3,315,131
Equity method investments	274,009	285,281
Goodwill	257,302	257,302
Other intangible assets (net of accumulated amortization of $90,014 and $56,409, respectively)	365,038	398,643
Other noncurrent assets, net	140,807	132,600
Noncurrent assets held for sale	0	84,961
Total assets	5,210,307	5,376,817
Current liabilities:
Accounts payable	494,792	587,898
Payable to affiliates	3,715	6,971
Accrued liabilities	115,095	131,407
Deferred revenue	11,060	7,518
Current liabilities held for sale	0	23,847
Other current liabilities	6,495	3,395
Current portion of long-term debt	6,000	5,525
Total current liabilities	637,157	766,561
Long-term debt	2,278,834	2,853,095
Deferred income taxes	55,789	46,585
Other noncurrent liabilities	38,548	38,495
Noncurrent liabilities held for sale	0	13,716
Commitments and contingencies (Note 14)
Redeemable preferred stock, $0.01 par value, $367,360 liquidation preference (authorized - 4,000 shares; issued - 350 and 0 shares, respectively)	359,658	0
SemGroup Corporation owners’ equity:
Common stock, $0.01 par value (authorized - 190,000 shares and 100,000 shares, respectively; issued - 79,270 and 79,708 shares, respectively)	786	786
Additional paid-in capital	1,615,969	1,770,117
Treasury stock, at cost (126 and 1,024 shares, respectively)	705	8,031
Accumulated deficit	(73,971)	(50,706)
Accumulated other comprehensive loss	(51,247)	(53,801)
Total SemGroup Corporation owners’ equity	1,490,832	1,658,365
Stockholders' Equity Attributable to Noncontrolling Interest	349,489	0
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	1,840,321	1,658,365
Total liabilities and owners’ equity	$ 5,210,307	$ 5,376,817

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Allowance for Doubtful Accounts Receivable, Current	$ 2,244	$ 2,628
Accumulated depreciation	607,903	444,842
Accumulated amortization on other intangible assets	$ 90,014	$ 56,409
Preferred Stock, Par or Stated Value Per Share	$ 0.01	$ 0.01
Preferred Stock, Liquidation Preference, Value	$ 367,360	$ 0
Preferred Stock, Shares Authorized	4,000,000	4,000,000
Preferred Stock, Shares Issued	350,000	0
Common Stock, Par or Stated Value Per Share	$ 0.01	$ 0.01
Common stock shares authorized	190,000,000	100,000,000
Common stock shares issued	79,270,000	79,708,000
Treasury Stock, Common, Shares	126,000	1,024,000

Consolidated Statements of Operations and Comprehensive Income (Loss) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenues:
Direct Financing Lease, Revenue									$ 17,549	$ 5,843	$ 0
Total Revenues	$ 611,863	$ 633,996	$ 595,794	$ 661,609	$ 606,806	$ 545,922	$ 473,089	$ 456,100	2,503,262	2,081,917	1,332,164
Expenses:
Cost of Goods Sold, Excluding Depreciation, Depletion, and Amortization									1,823,095	1,514,891	873,431
Operating									284,769	254,764	212,099
General and administrative									91,568	113,779	84,183
Depreciation and amortization									209,254	158,421	98,804
Loss (gain) on disposal or impairment, net	(1,438)	(383)	1,824	(3,566)	(30,468)	41,625	(234)	2,410	(3,563)	13,333	16,048
Total expenses	578,129	608,825	578,799	639,370	548,679	591,067	465,640	449,802	2,405,123	2,055,188	1,284,565
Earnings from equity method investments	16,179	14,528	14,351	12,614	15,120	17,367	17,753	17,091	57,672	67,331	73,757
Loss on issuance of common units by equity method investee									0	0	(41)
Operating income (loss)	49,913	39,699	31,346	34,853	73,247	(27,778)	25,202	23,389	155,811	94,060	121,315
Other expenses (income):
Interest expense									149,714	103,009	62,650
Loss on early extinguishment of debt									0	19,930	0
Foreign currency transaction loss (gain)									9,501	(4,709)	4,759
Loss on sale or impairment of non-operated equity method investment									0	0	30,644
Other expense (income), net									(2,380)	(4,632)	(1,269)
Total other expenses, net	40,410	33,935	37,685	44,805	39,487	28,574	11,966	33,571	156,835	113,598	96,784
Income (loss) from continuing operations before income taxes	9,503	5,764	(6,339)	(9,952)	33,760	(56,352)	13,236	(10,182)	(1,024)	(19,538)	24,531
Income tax expense (benefit)	6,531	(2,697)	(3,613)	23,083	31,141	(37,249)	3,625	95	23,304	(2,388)	11,268
Income (loss) from continuing operations									(24,328)	(17,150)	13,263
Income (loss) from discontinued operations, net of income taxes									0	0	(1)
Net income (loss)	2,972	8,461	(2,726)	(33,035)	$ 2,619	$ (19,103)	$ 9,611	$ (10,277)	(24,328)	(17,150)	13,262
Preferred Stock Dividends, Income Statement Impact	6,430	6,317	6,211	4,832					23,790	0	0
Net Income (Loss) Available to Common Stockholders, Basic	(5,879)	2,144	(8,937)	(37,867)					(50,539)	(17,150)	2,095
Less: net income attributable to noncontrolling interests	2,421	0	0	0					2,421	0	11,167
Net income (loss) attributable to SemGroup	$ 551	$ 8,461	$ (2,726)	$ (33,035)					(26,749)	(17,150)	2,095
Other comprehensive income (loss):
Currency translation adjustments									5,198	20,411	(14,224)
Other, net of income taxes									(2,644)	(298)	(1,128)
Total other comprehensive income (loss)									2,554	20,113	(15,352)
Comprehensive income (loss)									(21,774)	2,963	(2,090)
Less: comprehensive income attributable to noncontrolling interests									2,421	0	11,167
Comprehensive income (loss) attributable to SemGroup									$ (24,195)	$ 2,963	$ (13,257)
Net income (loss) attributable to SemGroup per common share (Note 19):
Basic	$ (0.08)	$ 0.03	$ (0.11)	$ (0.48)	$ 0.03	$ (0.25)	$ 0.15	$ (0.16)	$ (0.65)	$ (0.24)	$ 0.04
Diluted	$ (0.08)	$ 0.03	$ (0.11)	$ (0.48)	$ 0.03	$ (0.25)	$ 0.15	$ (0.16)	$ (0.65)	$ (0.24)	$ 0.04
Product [Member]
Revenue from Contract with Customer, Excluding Assessed Tax									$ 1,907,436	$ 1,621,918	$ 1,009,409
Service [Member]
Revenue from Contract with Customer, Excluding Assessed Tax									518,764	391,266	265,030
Other revenue [Member]
Revenue from Contract with Customer, Excluding Assessed Tax									$ 59,513	$ 62,890	$ 57,725

Consolidated Statements of Changes in Owners' Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Treasury Stock [Member]	Accumulated Deficit [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Noncontrolling Interest [Member]
Beginning Balance at Dec. 31, 2015	$ 1,196,356	$ 439	$ 1,217,255	$ (5,593)	$ (38,012)	$ (58,562)	$ 80,829
Net income (loss)	13,262				2,095		11,167
Other comprehensive income (loss), net of income taxes	(15,352)					(15,352)
Issuance of common stock	228,546	86	228,460
Acquisition of Rose Rock's noncontrolling interest	137,392	133	198,381				(61,122)
Distributions to noncontrolling interests	(32,133)						(32,133)
Dividends	(92,910)		(92,910)
Unvested dividend equivalent rights	587		521				66
Non-cash equity compensation	9,945		8,752				1,193
Issuance of common stock under compensation plans	1,237	1	1,236
Treasury Stock, Value, Acquired, Cost Method	(965)			(965)
Ending Balance at Dec. 31, 2016	1,445,965	659	1,561,695	(6,558)	(35,917)	(73,914)	0
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification	288		(2,073)		2,361
Net income (loss)	(17,150)				(17,150)
Other comprehensive income (loss), net of income taxes	20,113	0				20,113
Dividends	(129,925)		(129,925)
Unvested dividend equivalent rights	(1,033)		(1,033)
Non-cash equity compensation	10,066		10,066		0
Stock Issued During Period, Value, Acquisitions	330,341	124	330,217		0
Issuance of common stock under compensation plans	1,173	3	1,170
Treasury Stock, Value, Acquired, Cost Method	(1,473)			(1,473)
Ending Balance at Dec. 31, 2017	1,658,365	786	1,770,117	(8,031)	(50,706)	(53,801)	0
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification	11,513				11,513
Net income (loss)	(24,328)				(26,749)		2,421
Other comprehensive income (loss), net of income taxes	2,554	0	0	0	0	2,554	0
Distributions to noncontrolling interests	(2,932)						(2,932)
Dividends	(165,842)		(165,842)
Unvested dividend equivalent rights	(728)		(728)
Non-cash equity compensation	11,398		11,398
Noncontrolling Interest, Increase from Subsidiary Equity Issuance	350,000						350,000
Issuance of common stock under compensation plans	1,026	2	1,024
Treasury Stock, Retired, Cost Method, Amount		(2)		8,031	(8,029)
Treasury Stock, Value, Acquired, Cost Method	(705)			(705)
Ending Balance at Dec. 31, 2018	$ 1,840,321	$ 786	$ 1,615,969	$ (705)	$ (73,971)	$ (51,247)	$ 349,489

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Cash flows from operating activities:
Net income (loss)	$ (24,328)	$ (17,150)	$ 13,262
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation and amortization	209,254	158,421	98,804
Loss on disposal or impairment, net	(3,563)	13,333	16,048
Equity earnings from investments	(57,672)	(67,331)	(73,757)
Loss on issuance of common units by equity method investee	0	0	41
Loss on sale or impairment of non-operated equity method investment	0	0	30,644
Distributions from equity investments	57,625	66,748	76,442
Amortization and write down of debt issuance costs	7,651	6,221	7,561
Loss on early extinguishment of debt	0	19,930	0
Deferred tax expense (benefit)	8,311	(9,829)	8,447
Non-cash compensation expense	11,522	10,253	10,216
Provision for uncollectible accounts receivable, net of recoveries	390	165	(527)
Gain on pension curtailment	0	(3,008)	0
Inventory valuation adjustment	5,200	455	0
Foreign currency transaction loss (gain)	9,501	(4,709)	4,759
Changes in operating assets and liabilities (Note 22)	45,813	(33,023)	(21,966)
Net cash provided by operating activities	269,704	140,476	169,974
Cash flows from investing activities:
Capital expenditures	(390,734)	(462,713)	(312,456)
Proceeds from sale of equity method investment and other long-lived assets	1,958	314,821	151
Investments in non-consolidated subsidiaries	(7,781)	(26,444)	(4,188)
Payments to acquire business, net of cash acquired	0	294,239	0
Proceeds from sale of common units of equity method investee	0	0	60,483
Proceeds from Divestiture of Businesses, Net of Cash Divested	147,787	0	0
Distributions from equity method investments in excess of equity in earnings	19,100	28,774	27,726
Net cash provided by (used in) investing activities	(229,670)	(439,801)	(228,284)
Cash flows from financing activities:
Debt issuance costs	(4,720)	(11,116)	(7,728)
Borrowings on credit facilities and issuance of senior unsecured notes	1,258,500	1,525,377	382,500
Principal payments on debt and other obligations	(1,839,894)	(1,052,428)	(396,890)
Debt extinguishment costs	0	(16,293)	0
Proceeds from Noncontrolling Interests	350,000	0	0
Distributions to noncontrolling interests	(2,932)	0	(32,133)
Proceeds from Issuance of Preferred Stock and Preference Stock	342,299	0	0
Repurchase of common stock for payment of statutory taxes due on equity-based compensation	(705)	(1,473)	(965)
Dividends paid	(148,482)	(129,925)	(92,910)
Proceeds from issuance of common stock under employee stock purchase plan	930	1,114	1,010
Proceeds from issuance of common shares, net of offering costs	0	0	223,025
Net cash provided by (used in) financing activities	(45,004)	315,256	75,909
Effect of exchange rate changes on cash and cash equivalents	(2,074)	3,552	(1,479)
Change in cash and cash equivalents	(7,044)	19,483	16,120
Cash and cash equivalents at beginning of period	93,699	74,216	58,096
Cash and cash equivalents at end of period	$ 86,655	$ 93,699	$ 74,216

Overview

12 Months Ended

Dec. 31, 2018

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Overview

OVERVIEW

SemGroup Corporation is a Delaware corporation headquartered in Tulsa, Oklahoma that provides diversified services for end-users and consumers of crude oil, natural gas, natural gas liquids and refined products.

The accompanying consolidated financial statements include the activities of SemGroup Corporation and its subsidiaries. The terms “we,” “our,” “us,” “the Company” and similar language used in these notes to consolidated financial statements refer to SemGroup Corporation and its subsidiaries.

At December 31, 2018, our operating and reportable segments include the following:


•	our U.S. Liquids segment operates crude oil pipelines, truck transportation, storage, terminals and marketing businesses in the U.S. Additionally, we store, blend and transport refinery products and refinery feedstocks via pipeline, barge, rail, truck and ship and operate a residual fuel oil storage terminal in the U.S. Gulf Coast;


•	our U.S. Gas segment provides natural gas gathering, processing and marketing services. U.S. Gas aggregates gas supplies from the wellhead and provides various services to producers that condition the wellhead gas production for downstream markets; and


•	our Canada segment provides natural gas gathering and processing services in Alberta, Canada and owns working interests in, and operates, a network of natural gas gathering and transportation pipelines and natural gas processing plants.

Additionally, we own an 11.78% interest in the general partner of NGL Energy Partners LP ("NGL Energy") (NYSE: NGL). See Note 4 for discussion of the disposal of our Mexican asphalt business and our U.K. operations during the year ended December 31, 2018.

Consolidation And Basis Of Presentation	12 Months Ended
Consolidation And Basis Of Presentation	Dec. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Consolidation and Basis of Presentation	CONSOLIDATION AND BASIS OF PRESENTATION The accompanying consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States. Consolidated subsidiaries Our consolidated financial statements include the accounts of our controlled subsidiaries. All significant transactions between our consolidated subsidiaries have been eliminated. Outside ownership interests in consolidated subsidiaries are reported as noncontrolling interests in the consolidated financial statements. Proportionally consolidated assets Our Canada segment owns undivided interests in certain natural gas gathering and processing assets, for which we record only our proportionate share of the assets on the consolidated balance sheets. The net book value of the property, plant and equipment recorded by us associated with these undivided interests is approximately $570.8 million at December 31, 2018. We serve as operator of these facilities and incur the costs of operating the facilities (recorded as operating expenses in the consolidated statements of operations) and charge the other owners, which are also customers, for their proportionate share of the costs (recorded as other revenue in the consolidated statements of operations). Equity method investments We own a 51% interest in White Cliffs Pipeline, LLC ("White Cliffs"), which we account for under the equity method as the other owners have substantive rights to participate in its management. White Cliffs is included in our U.S. Liquids segment. We own an 11.78% interest in the general partner of NGL Energy Partners LP (NYSE: NGL) ("NGL Energy") which we account for under the equity method. Our investment in NGL Energy is included in Corporate and Other for segment reporting.

Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2018

Accounting Policies [Abstract]

Summary of Signifcant Accounting Policies

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES

USE OF ESTIMATES—The preparation of financial statements in conformity with accounting principles generally accepted in the United States requires management to make estimates and assumptions that affect the amounts and disclosures in the financial statements. Our significant estimates include, but are not limited to: (1) allowances for doubtful accounts receivable; (2) estimated useful lives of assets, which impact depreciation and amortization; (3) estimated fair values used in impairment tests; (4) fair values of derivative instruments; (5) valuation allowances for

deferred tax assets; and (6) accrual and disclosure of contingent losses. Although management believes these estimates are reasonable, actual results could differ materially from these estimates.

CASH AND CASH EQUIVALENTS—Cash includes currency on hand and demand and time deposits with banks or other financial institutions. Cash equivalents include highly liquid investments with maturities of three months or less at the date of purchase. Balances at financial institutions may exceed federally insured limits.

In June 2016, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update ("ASU") 2016-13, "Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments", which introduces new guidance for estimating credit losses on certain types of financial instruments based on expected losses and the timing of the recognition of such losses. For public entities, this ASU is effective for annual periods beginning after December 15, 2019, and interim periods within those years and early adoption is permitted in the year prior to the effective date. We will adopt this guidance in the first quarter of 2020. The impact is not expected to be material.

INVENTORY—Inventory consists of crude oil and is valued at the lower of cost or net realizable value, with cost generally determined using the weighted-average method. The cost of inventory includes applicable transportation costs.

We enter into exchanges with third parties whereby we acquire products that differ in location, grade, or delivery date from products we have available for sale. These exchanges are valued at cost, and although a transportation, location or product differential may be recorded, generally no gain or loss is recognized.

During the year ended December 31, 2018 and 2017, our U.S. Liquids segment recorded non-cash charges of $5.2 million and $0.5 million, respectively, to write-down crude oil inventory to the lower of cost or net realizable value. Asphalt inventory related to our former Mexican operations of $15.6 million was classified as held for sale at December 31, 2017.

PROPERTY, PLANT AND EQUIPMENT—Property, plant and equipment is recorded at cost. We capitalize costs that extend or increase the future economic benefits of property, plant and equipment, and expense maintenance costs that do not. When assets are disposed of, their cost and related accumulated depreciation are removed from the balance sheet, and any resulting gain or loss is recorded as a gain or loss on disposal or impairment in the consolidated statements of operations and comprehensive income (loss).

Our Canada segment operates plants which periodically undergo planned major maintenance activities, typically occurring every four to five years. Planned major maintenance projects that do not increase the overall life or capacity of the related assets are recorded in operating expense as incurred, whereas major maintenance activity costs that materially increase the life or capacity of the underlying assets are capitalized. When maintenance expenses are recoverable from the producers who use the plants, they are recorded as revenue, and typically include a 10% overhead fee.

Depreciation is calculated primarily using the straight-line method over the following estimated useful lives:



Pipelines and related facilities	10 – 31 years
Storage and terminal facilities	10 – 25 years
Natural gas gathering and processing facilities	10 – 31 years
Trucking equipment and other	3 – 7 years
Office property and equipment	3 – 31 years

Construction in process is reclassified to the fixed asset categories above and depreciation commences once the asset has been placed in-service.

owned by us in facilities operated by us is recorded at historical cost, is included in property, plant and equipment in the consolidated balance sheets, and is not depreciated. We also own linefill in third-party facilities, which is included in inventory on the consolidated balance sheets.

IMPAIRMENT OF LONG-LIVED ASSETS—We test long-lived asset groups for impairment when events or circumstances indicate that the net book value of the asset group may not be recoverable. We test an asset group for impairment by estimating the undiscounted cash flows expected to result from its use and eventual disposition. If the estimated undiscounted cash flows are lower than the net book value of the asset group, we then estimate the fair value of the asset group and record a reduction to the net book value of the assets and a corresponding impairment loss.

GOODWILL—We test goodwill for impairment on an annual basis, or more often if circumstances warrant, by estimating the fair value of the reporting unit to which the goodwill relates and comparing this fair value to the net book value of the reporting unit. If fair value is less than net book value, we reduce the book value accordingly and record a corresponding impairment loss. Our policy is to test goodwill for impairment on October 1 of each year.

FINITE-LIVED INTANGIBLE ASSETS—Finite-lived intangible assets are stated at cost, net of accumulated amortization, which is recorded on a straight-line or accelerated basis over the life of the asset. We review amortizable intangible assets for impairment whenever events or changes in circumstances indicate that the carrying amount of such assets may not be recoverable. If such a review should indicate that the carrying amount of amortizable intangible assets is not recoverable, we reduce the carrying amount of such assets to fair value.

EQUITY METHOD INVESTMENTS—We account for an investment under the equity method when we have significant influence over, but not control of, the significant operating decisions of the investee. Under the equity method, we record in the consolidated statements of operations our share of the earnings or losses of the investee, with a corresponding adjustment to the investment balance on our consolidated balance sheet. When we receive a distribution from an equity method investee, we record a corresponding reduction to the investment balance. When an equity method investee issues additional ownership interests which dilute our ownership interest, we recognize a gain or loss in our consolidated statements of operations.

We assess our equity method investments for impairment when circumstances indicate that the carrying value may not be recoverable and record an impairment when a decline in value is considered to be other than temporary.

For equity method investments for which we do not expect financial information to be consistently available on a timely basis to apply the equity method currently, our policy is to apply the equity method consistently on a one-quarter lag.

DEBT ISSUANCE COSTS—Costs incurred in connection with the issuance of long-term debt are reported as a reduction to the carrying value of the associated debt instrument and are amortized to interest expense using the straight-line method over the term of the related debt. Use of the straight-line method of amortization does not differ materially from the “effective interest” method.

Capitalized loan fees related to our revolving credit facility are presented as other noncurrent assets.

COMMODITY DERIVATIVE INSTRUMENTS—We generally record the fair value of commodity derivative instruments on the consolidated balance sheets and the change in fair value as an increase or decrease to product revenue.

As shown in Note 10, the fair value of commodity derivatives at December 31, 2018 and 2017 are recorded to other current assets or other current liabilities on the consolidated balance sheets. Related margin deposits are recorded to other current assets or other current liabilities on the consolidated balance sheets. Margin deposits are not generally netted against derivative assets or liabilities.

The fair value of a derivative contract is determined based on the nature of the transaction and the market in which the transaction was executed. Quoted market prices, when available, are used to value derivative transactions. In situations where quoted market prices are not readily available, we estimate the fair value using other valuation techniques that reflect the best information available under the circumstances. Fair value measurements of derivative assets include consideration of counterparty credit risk. Fair value measurements of derivative liabilities include consideration of our creditworthiness.

We have elected “normal purchase” and “normal sale” treatment for certain commitments to purchase or sell petroleum products at future dates. This election is only available when a transaction that would ordinarily meet the definition of a derivative but instead is expected to result in physical delivery of product over a reasonable period in the normal course of business and is not expected to be net settled. Agreements accounted for under this election are not recorded at fair value; instead, the transaction is recorded when the product is delivered.

CONTINGENT LOSSES—We record a liability for a contingent loss when it is probable that a loss has been incurred and the amount of the loss can be reasonably estimated. We record attorneys’ fees incurred in connection with a contingent loss at the time the fees are incurred. We do not record liabilities for attorneys’ fees that are expected to be incurred in the future.

ASSET RETIREMENT OBLIGATIONS—Asset retirement obligations include legal or contractual obligations associated with the retirement of long-lived assets, such as requirements to incur costs to dispose of equipment or to remediate the environmental impacts of the normal operation of the assets. We record liabilities for asset retirement obligations when a known obligation exists under current law or contract and when a reasonable estimate of the value of the liability can be made.

PREFERRED STOCK—Preferred stock is classified as debt, equity or mezzanine equity based on its redemption features. Preferred stock with redemption features outside of the control of the issuer, such as contingent redemption features, is classified as mezzanine equity. Preferred stock with mandatory redemption features is classified as debt. Preferred stock with no redemption features, or redemption features over which the issuer has control, is classified as equity.

REVENUE RECOGNITION—Product sales revenues are recognized at the time control of the product transfers to the purchaser, which typically occurs upon receipt of the product by the purchaser. Service revenues are generally recognized overtime as the service is performed. Certain revenue transactions are reported on a net basis, including certain buy/sell transactions (see “Purchases and Sales of Inventory with the Same Counterparty”). Other revenue primarily represents operating cost recovery from working interest owners, who are also customers, in certain processing plants and is recorded when earned in accordance with the terms of related agreements. Taxes collected from customers and remitted to governmental authorities are recorded on a net basis (excluded from revenue).

In May 2014, the FASB issued ASU 2014-09, “Revenue from Contracts with Customers”, as amended, which supersedes nearly all existing revenue recognition guidance under U.S. GAAP. The core principle of ASU 2014-09 is to recognize revenues when promised goods or services are transferred to customers in an amount that reflects the consideration to which an entity expects to be entitled for those goods or services. ASU 2014-09 defines a five step process to achieve this core principle and, in doing so, more judgment and estimates may be required within the revenue recognition process than were required under previous U.S. GAAP.

On January 1, 2018, we adopted the guidance of ASU 2014-09, codified as Accounting Standards Codification 606 - Revenue from Contracts with Customers (“ASC 606”), using a modified retrospective approach. Upon adoption, a reduction to accumulated deficit of $11.5 million was recorded to reflect the impact of adoption related to uncompleted contracts at the date of adoption. The impacts of adoption to the current period results are as follows (in thousands):



	December 31, 2018
	Under ASC 606			Under ASC 605			Increase/(Decrease)
Accounts receivable, net	$	562,214		$	562,057		$	157
Other noncurrent assets	$	140,807		$	119,911		$	20,896
Other current liabilities	$	6,495		$	6,538		$	(43	)
Deferred income taxes	$	55,789		$	50,045		$	5,744
Accumulated deficit	$	(73,971	)	$	(89,324	)	$	15,353



	Year Ended December 31, 2018
	Under ASC 606			Under ASC 605			Increase/(Decrease)
Revenue	$	2,503,262		$	2,483,962		$	19,300
Cost of sales	$	1,823,095		$	1,808,129		$	14,966
General and administrative expense	$	91,568		$	91,168		$	400
Income tax benefit	$	23,304		$	23,209		$	95
Net loss	$	(24,328	)	$	(28,167	)	$	3,839



Net loss attributable to common shareholders	$	(50,539	)	$	(54,378	)	$	3,839
Net loss per common share:
Basic	$	(0.65	)	$	(0.70	)	$	0.05
Diluted	$	(0.65	)	$	(0.70	)	$	0.05

•

Changes to revenue primarily relate to the timing of recognition of deficiencies on take-or-pay agreements for which there is a contractual make-up period and a change to reporting certain gas gathering and processing fees as revenue rather than a reduction of cost of sales. Under ASC 605 - Revenue (“ASC 605”), revenue related to deficiencies with a make-up period was deferred until the contractual right to make-up a deficiency expired. Under ASC 606, we recognize all or a portion of revenue related to deficiencies before the make-up period expires if we determine that it is probable that the customer will not make-up all or some of its deficient volumes, for example if there is insufficient capacity to make up the deficient volumes. This may lead to earlier recognition of deficiency revenues under ASC 606 as compared with ASC 605.


•	Changes to cost of sales are due to how certain gathering and processing fees related to percentage of proceeds contracts are treated as revenues rather than reductions to purchase price of commodities (cost of sales).

•

Changes to accounts receivable, net and noncurrent receivables (included in other noncurrent assets on the condensed consolidated balance sheets) primarily relate to the timing of recognizing take-or-pay deficiencies with make-up rights as discussed above. Noncurrent receivables relate to contracts for which we do not have the right to bill the customer for deficiencies until the contract expiration date.


•	Changes to other noncurrent assets include success fee payments to third parties for certain contracts which were expensed as incurred under ASC 605, but which have been recognized as assets under ASC 606 and are amortized to general and administrative expense in the consolidated statement of operations and comprehensive income (loss).


•	Changes to deferred income taxes primarily relate to the deferred tax impact of adoption entries.


•	Changes to retained earnings are due to the impact of adoption at January 1, 2018, as described above, and cumulative differences in net income through December 31, 2018.

See Note 18 for additional information.

COSTS OF PRODUCTS SOLD—Costs of products sold consists of the cost to purchase the product, the cost to transport the product to the point of sale, and the cost to store the product until it is sold.

PURCHASES AND SALES OF INVENTORY WITH THE SAME COUNTERPARTY—We routinely enter into transactions to purchase inventory from, and sell inventory to, the same counterparty. Such transactions that are entered into in contemplation of one another are recorded on a net basis.

CURRENCY TRANSLATION—The consolidated financial statements are presented in U.S. dollars. Our segments operated in four countries, until the disposal of our U.K. and Mexican operations in early 2018, and each segment has identified a “functional currency,” which is the primary currency in the environment in which the segment operates. The functional currencies included the U.S. dollar, the Canadian dollar, the British pound sterling, and the Mexican peso. Subsequent to the disposal of our U.K. and Mexican operations, our functional currencies are the U.S. and Canadian dollars.

At the end of each reporting period, the assets and liabilities of each segment are translated from its functional currency to U.S. dollars using the exchange rate at the end of the month. The monthly results of operations of each segment are generally translated from its functional currency to U.S. dollars using the average exchange rate during the month. Changes in exchange rates result in currency translation gains and losses, which are recorded within other comprehensive income (loss).

Certain segments also enter into transactions in currencies other than their functional currencies. At the end of each reporting period, each segment re-measures the related receivables, payables, and cash to its functional currency using the exchange rate at the end of the period. Changes in exchange rates between the time the transactions were entered into and the end of the reporting period result in currency transaction gains or losses, which are recorded in the consolidated statements of operations.

INCOME TAXES—Deferred income taxes are accounted for under the liability method, which takes into account the differences between the basis of the assets and liabilities for financial reporting purposes and amounts recognized for income tax purposes. We record valuation allowances on deferred tax assets when, in the opinion of management, it is more likely than not that the asset will not be recovered.

We monitor uncertain tax positions and we recognize tax benefits only when management believes the relevant tax positions would more likely than not be sustained upon examination. We record any interest and any penalties related to income taxes within income tax expense in the consolidated statements of operations.

In October 2016, the FASB issued ASU 2016-16, “Income Taxes (Topic 740): Intra-Entity Transfers of Assets Other Than Inventory”, which requires an entity to recognize the income tax consequences of an intra-entity transfer of an asset other than inventory when the transfer occurs. We adopted this guidance in the first quarter of 2018. The impact was not material.

In February 2018, the FASB issued ASU 2018-02, “Income Statement - Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income”, which allows a reclassification from accumulated other comprehensive income to retained earnings for stranded tax effects resulting from the Tax Cuts and Jobs Act. For public entities, this ASU is effective for annual periods beginning after December 15, 2018, and interim periods within those years and early adoption is permitted in the year prior to the effective date. We adopted this guidance in the first quarter of 2019. We recorded a $10.9 million adjustment to retained earnings upon adoption.

RECLASSIFICATIONS—Certain reclassifications have been made to conform prior year balances to the current year presentation.

In March 2017, the FASB issued ASU 2017-07, “Compensation - Retirement Benefits (Topic 715): Improving the Presentation of Net Periodic Pension Cost and Net Periodic Post-retirement Benefit Cost”, which requires that an employer disaggregate the service cost component from other components of net benefit cost. This ASU also provides explicit guidance on how to present the service cost component and the other components of net benefit cost in the income statement and allows only the service cost component of net benefit cost to be eligible for capitalization. We adopted this guidance retrospectively in the first quarter of 2018. For the years ended December 31, 2017 and 2016, we reclassified $3.2 million, of non-service pension gains and $0.3 million of non-service pension costs, respectively, from “general and administrative expense” to “other expense (income)”.

In May 2017, the FASB issued ASU 2017-09, “Compensation - Stock Compensation (Topic 718): Scope of Modification Accounting”, to provide clarity and reduce diversity in practice in determining which changes to terms or conditions of a share-based payment award require an entity to apply modification accounting under Accounting Standards Codification Topic 718. We adopted this guidance in the first quarter of 2018. The impact was not material.

NONCONTROLLING INTEREST—Noncontrolling interests represents a 49% interest in our consolidated subsidiary, Maurepas Pipeline, LLC in the form of Class B shares of Maurepas Pipeline, LLC. The Class B shares provide for a monthly preference on Maurepas Pipeline, LLC distributions for the owners.

COMPREHENSIVE INCOME (LOSS) AND ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS)—Comprehensive income (loss) is defined as a change in equity of a business enterprise during a period from transactions and other events and circumstances from non-owner sources and includes all changes in equity during a period except those resulting from investments by owners and distributions to owners. Our comprehensive income (loss) includes currency translation adjustments and changes in the funded status of pension benefit plans.

OTHER RECENT ACCOUNTING PRONOUNCEMENTS— On August 27, 2018, the FASB issued ASU 2018-13, “Fair Value Measurement (Topic 820): Disclosure Framework—Changes to the Disclosure Requirements for Fair Value Measurement”, which modifies the disclosure requirements in Topic 820 by removing, adding or modifying certain fair value measurement disclosures. For public entities, this ASU is effective for annual periods beginning after December 15, 2019, and interim periods therein. Early adoption is permitted. We will adopt this guidance in the first quarter of 2020. The impact is not expected to be material.

In August 2016, the FASB issued ASU 2016-15, “Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments (a consensus of the Emerging Issues Task Force)”, to reduce diversity in practice in how certain transactions are classified in the statement of cash flows. The update addresses eight different transaction types and clarifies how to classify each in the statement of cash flows, where previously there was unclear or no specific guidance. We adopted this guidance in the first quarter of 2018. The impact was not material.

In February 2016, the FASB issued ASU 2016-02, “Leases (Topic 842)”, as amended, which amends the existing lease guidance to require lessees to recognize assets and liabilities on the balance sheet for the rights and obligations created by operating and finance leases and to disclose additional quantitative and qualitative information about leasing arrangements. This ASU, as amended, also provides clarifications surrounding the presentation of the effects of leases in the income statement and statement of cash flows. For public entities, this ASU will be effective for annual periods beginning after December 15, 2018, and interim periods within those years. We have elected the package of practical expedients such that we will not reassess whether any expired or existing contracts contain leases, we will not reassess the lease classification for any expired or existing leases and we will not reassess initial direct costs for any leases. Additionally, we have elected the practical expedient not to reassess certain land easements. As such, certain storage tank, pipeline leases and land easements, which are not currently treated as leases, maybe become leases as these agreements are renewed or modified depending on the terms of the renewal or modification. Additionally, the classification for existing leases may change as agreements are renewed or modified. We adopted the standard at January 1, 2019, and recorded approximately $100 million of right of use assets and lease liabilities. We recognized a cumulative-effect adjustment to the opening balance of retained earnings of approximately $0.2 million as allowed by ASU 2018-11, “Leases (Topic 842): Targeted Improvements”.

Disposals of Long-Lived Assets

12 Months Ended

Dec. 31, 2018

Disposals And Impairments Of Long-Lived Assets [Abstract]

Disposals of Long-Lived Assets

DISPOSALS OR IMPAIRMENTS OF LONG-LIVED ASSETS

Year ended December 31, 2018

On January 5, 2018, we entered into a definitive agreement to sell our Mexican asphalt business. The sale closed on March 15, 2018, for $70.7 million. We recorded a pre-tax gain on disposal of $1.6 million for the year ended December 31, 2018. The Mexican asphalt business contributed $2.3 million of pre-tax income for the year ended December 31, 2018, excluding the gain on disposal. At December 31, 2017, the assets and liabilities of the Mexican asphalt business were written down to net realizable value by recording an impairment of $13.5 million, including the impact of a deferred foreign currency translation loss of $30.9 million, and classified as held for sale. The Mexican asphalt business contributed a pre-tax loss of $8.2 million for the year ended December 31, 2017, including the write-down to net realizable value. At December 31, 2017, the Mexican assets and liabilities held for sale included $29.4 million of property, plant and equipment, $34.9 million of current assets and $19.4 million of current liabilities, prior to the write-down to net realizable value.

On February 23, 2018, we entered into an agreement to sell our U.K. operations, SemLogistics. The sale closed on April 12, 2018, for $73.1 million. We recorded a pre-tax gain on disposal of $0.4 million for the year ended December 31, 2018. The U.K. business contributed pre-tax income of $5.4 million for the year ended December 31, 2018, excluding the gain on disposal. At December 31, 2017, the assets and liabilities of the U.K. operations were written down to net realizable value by recording an impairment of $76.7 million, including the impact of a deferred foreign currency translation loss of $22.8 million, and classified as held for sale. The U.K. business contributed a pre-tax loss of $73.0 million for the year-ended December 31, 2017, including the write-down to net realizable value. At December 31, 2017, the U.K. assets and liabilities held for sale included $136.8 million of property, plant and equipment, $3.1 million of current assets and $4.4 million of current liabilities, prior to the write-down to net realizable value.

Year ended December 31, 2017

The following amounts are included in "loss on disposal or impairment, net" on our consolidated statement of operations and comprehensive income (loss) for the year ended December 31, 2017 (in thousands):



	Segment	Loss/(Gain)
Write-down of Mexican asphalt business to net realizable value	Corporate and Other	$	13,511
Write-down U.K. operations to net realizable value	Corporate and Other	76,661
Sherman natural gas gathering and processing asset impairment	U.S. Gas	30,985
Crude oil trucking goodwill impairment (Note 9)	U.S. Liquids	26,628
Crude oil trucking intangible asset impairment (Note 9)	U.S. Liquids	12,087
Gain on sale of Glass Mountain Pipeline LLC (Note 6)	U.S. Liquids	(150,266		)
Other		3,727
Loss on disposal or impairment, net		$	13,333

At December 31, 2017, we recorded a $31.0 million impairment of our Sherman, Texas natural gas gathering and processing assets of our U.S. Gas segment. Evaluation of capital raising alternatives indicated that the carrying value of our Sherman, Texas assets might be in excess of fair value. We compared the forecasted undiscounted cash flows for the assets to the carrying value of the assets, which indicated that the carrying value of assets was impaired. We used an income approach, based on a discounted cash flow model, to estimate the fair value of the assets and recorded a non-cash impairment.

Impairments are based on unobservable inputs and considered to be Level 3 measurements. See Note 6 for discussion of the sale of our equity method investment in Glass Mountain Pipeline LLC ("Glass Mountain"). See Note 9 for discussion of impairment of goodwill and finite-lived intangible assets recorded by our U.S. Liquids segment.

Year ended December 31, 2016

There were no significant disposals or impairments of long-lived assets during the year ended December 31, 2016. See Note 6 for discussion of our sale of NGL Energy limited partner units accounted for under the equity method. See Note 9 for discussion of goodwill impairment related to our U.S. Gas segment.

Acquisitions	12 Months Ended
Acquisitions	Dec. 31, 2018
Acquisitions [Abstract]
Business Combination Disclosure [Text Block]	ACQUISITIONS Year ended December 31, 2018 There were no significant acquisitions during the year ended December 31, 2018. Year ended December 31, 2017 On July 17, 2017, we acquired Houston Fuel Oil Terminal Company (“HFOTCO”), one of the largest oil terminals in the U.S., for a purchase price paid in two payments. The first payment consisted of $297.8 million in cash funded from our revolving credit facility, the issuance of approximately 12.4 million shares of our Class A common stock with an acquisition date fair value of $330 million, and the assumption of existing HFOTCO debt of approximately $766 million. On April 17, 2018, we made the final payment related to the HFOTCO acquisition in the amount of $579.6 million. The payment was funded through revolving credit facility borrowings and cash on hand. From the acquisition date through December 31, 2017, HFOTCO contributed $76.9 million of revenue and $2.4 million of net loss to our consolidated financial results. Our results for the year ended December 31, 2017, include $19.2 million of acquisition related expenses, which are included in "general and administrative expenses" in our consolidated statement of operations and comprehensive income (loss). Included in the results of HFOTCO for the post acquisition period is a gain of $3.0 million related to the curtailment of HFOTCO’s defined benefit pension plan. Subsequent to the acquisition, SemGroup closed the plan to new members and stopped the accrual of future benefits under the plan to better align HFOTCO with SemGroup’s compensation strategy. Accordingly, the pension liability assumed at acquisition of $10.0 million was reduced to $7.0 million as of December 31, 2017. HFOTCO is included in the U.S. Liquids segment. Year ended December 31, 2016 On September 30, 2016, we completed the acquisition of the outstanding common limited partner interests of Rose Rock Midstream, L.P. ("Rose Rock") which we did not already own (the "Merger"). We issued 13.1 million common shares as consideration and recorded a reduction to equity for $5.3 million of fees associated with the issuance. In addition, we recorded a reduction to our deferred tax liabilities and offsetting increase to additional paid-in capital of $143.3 million associated with the transaction. This non-cash adjustment represents the deferred tax impact of the difference between the book value of the noncontrolling interests acquired and the tax basis which is stepped-up to the fair market value of the consideration, which includes the common shares issued and the assumption of liabilities associated with the noncontrolling interests. We accounted for the Merger in accordance with FASB Accounting Standards Codification 810, Consolidation — Overall — Changes in a Parent’s Ownership Interest in a Subsidiary. As SemGroup controlled Rose Rock both before and after the Merger, the changes in SemGroup’s ownership interest in Rose Rock were accounted for as an equity transaction and no gain or loss was recognized in SemGroup’s consolidated statements of operations and comprehensive income (loss) as a result of the Merger. Subsequent to the Merger, Rose Rock was a wholly owned subsidiary of SemGroup. Substantially all of Rose Rock's assets were pledged as collateral under its senior secured revolving credit facility agreement which was terminated following the Merger. Substantially all of Rose Rock's assets are now pledged as collateral under SemGroup's senior secured revolving credit facility. Rose Rock's senior unsecured notes were assumed by SemGroup.

Equity Method Investments

12 Months Ended

Dec. 31, 2018

Equity Method Investments and Joint Ventures [Abstract]

Equity Method Investments

EQUITY METHOD INVESTMENTS

Our equity method investments consist of the following (in thousands):



	December 31,
	2018		2017
White Cliffs	$	255,043	$	266,362
NGL Energy	18,966		18,919
Total equity method investments	$	274,009	$	285,281

Our earnings from equity method investments consist of the following (in thousands):



	Year Ended December 31,
	2018		2017			2016
White Cliffs	$	57,625	$	59,851		$	69,007
Glass Mountain	—		7,494			2,562
NGL Energy⁽¹⁾	47		(14		)	2,188
Total earnings from equity method investments	$	57,672	$	67,331		$	73,757

(1) Excluding a loss on issuance of common units of $41.0 thousand for the year ended December 31, 2016.

Cash distributions received from equity method investments consist of the following (in thousands):



	Year Ended December 31,
	2018		2017		2016
White Cliffs	$	76,725	$	77,511	$	88,839
Glass Mountain	—		18,011		10,456
NGL Energy	—		—		4,873
Total cash distributions received from equity method investments	$	76,725	$	95,522	$	104,168

White Cliffs

We own a 51% interest in White Cliffs, which we account for under the equity method. The equity in earnings of White Cliffs for the years ended December 31, 2018, 2017 and 2016, reported in our consolidated statements of operations and comprehensive income (loss), is less than 51% of the net income of White Cliffs for the same period. This is primarily due to certain general and administrative expenses we incur in managing the operations of White Cliffs that the other members are not obligated to share. In addition, our equity in earnings is also impacted by the elimination of revenue on the sale of inventory to White Cliffs. Revenue related to inventory transactions with White Cliffs is deferred until a sale of the inventory has been made with a third party.

The members of White Cliffs are required to contribute capital to White Cliffs to fund various projects. For the years ended December 31, 2018, 2017 and 2016, we contributed $6.5 million, $1.4 million and $2.2 million, respectively, to fund White Cliffs capital projects. In 2018, we announced that we will convert one of the White Cliffs 12-inch carrier pipelines from crude service to natural gas liquids service. Remaining contributions related to the conversion project will be paid in 2019 and are expected to total $27.2 million. The project is expected to be completed during the fourth quarter of 2019.

Our membership interest in White Cliffs is significant as defined by Securities and Exchange Commission’s Regulation S-X Rule 1-02(w). Accordingly, as required by Regulation S-X Rule 3-09, we have included the audited financial statements of White Cliffs as of December 31, 2018 and 2017 and for each of the three years in the period ended December 31, 2018 as an exhibit to this Form 10-K.

Glass Mountain

On December 22, 2017, we completed the sale of our equity method investment in Glass Mountain for $300 million, subject to working capital and other adjustments. For the year ended December 31, 2017, we recorded a pre-tax gain on disposal of $150.3 million, which was reported in "loss (gain) on disposal or impairment, net" in our consolidated statement of operations and comprehensive income (loss). Proceeds from the sale were used to repay borrowings on SemGroup's revolving credit facility. For the year ended December 31, 2018, we recorded an incremental gain of $1.1 million related to customary post-closing adjustments related to the prior year sale of our equity interest in Glass Mountain.

NGL Energy

At December 31, 2018, we held an 11.78% interest in the general partner of NGL Energy which is being accounted for under the equity method in accordance with ASC 323-30-S99-1, as our ownership is in excess of the 3 to 5 percent interest which is generally considered to be more than minor.

The general partner of NGL Energy is not a publicly traded company. The information below pertains to our general partner interest, and previously held limited partner interest, in NGL Energy.

NGL Energy unit issuance and sale of NGL Energy units

During the year ended December 31, 2016, we sold 4,652,568 NGL Energy limited partner units for $13.00 per unit, or $60.5 million, and recorded a $9.1 million gain on disposal. Subsequent to this disposal, we no longer hold a limited partner interest in NGL Energy. Gain on disposal of NGL Energy limited partner units is included in "loss on sale or impairment of non-operated equity method investment" in our consolidated statements of operations and comprehensive income (loss).

During the year ended December 31, 2016, our limited partnership interest was diluted in connection with an NGL Energy common unit issuance. Accordingly, we recorded a non-cash loss of $41.0 thousand for the year ended December 31, 2016 related to this transaction, which is included in "loss on issuance of common units by equity method investee" in our consolidated statements of operations and comprehensive income (loss).

Other-than-temporary impairment of equity method investment in NGL Energy

During the year ended 2016, we recorded an impairment of $39.8 million to our investment in the limited partner units of NGL Energy subsequent to NGL Energy's April 21, 2016 announcement of a reduction in its quarterly distribution and lowering of financial performance guidance. These units were subsequently sold in the second quarter of 2016. The impairment was included in "loss on sale or impairment of non-operated equity method investment" in our consolidated statements of operations and comprehensive income (loss).

Other Assets

12 Months Ended

Dec. 31, 2018

Other Assets [Abstract]

Other Assets

OTHER ASSETS

Other current assets consist of the following (in thousands):



	December 31,
	2018		2017
Prepaid expenses	$	8,379	$	8,746
Other	8,885		5,551
Total other current assets	$	17,264	$	14,297

Other noncurrent assets consist of the following (in thousands):



	December 31,
	2018		2017
Capitalized loan fees	$	6,074	$	8,774
Net investment in direct financing lease	69,222		67,825
Deferred tax asset	25,307		33,792
Other	40,204		22,209
Total other noncurrent assets, net	$	140,807	$	132,600

Net investment in direct financing lease, included in the table above, relates to our HFOTCO operations' lease of certain land, tanks and a barge dock which are accounted for as a direct financing lease. The assets are leased through 2025. At December 31, 2018, minimum lease payments to be received for each of the five succeeding fiscal years and thereafter are as follows (in thousands):



For the year ending:
December 31, 2019	$	13,732
December 31, 2020	13,031
December 31, 2021	12,800
December 31, 2022	12,804
December 31, 2023	12,808
Thereafter	18,151
Total minimum lease payments	$	83,326

Property, Plant and Equipment

12 Months Ended

Dec. 31, 2018

Property, Plant and Equipment [Abstract]

Property, Plant and Equipment

PROPERTY, PLANT AND EQUIPMENT

Property, plant and equipment consists of the following (in thousands):



	December 31,
	2018			2017
Land	$	308,166		$	273,168
Pipelines and related facilities	1,023,502			926,799
Storage and terminal facilities	1,247,115			1,111,001
Natural gas gathering and processing facilities	1,055,305			940,130
Linefill	27,972			25,747
Trucking equipment and other	45,567			45,162
Office property and equipment	69,498			63,052
Construction-in-progress	288,104			374,914
Property, plant and equipment, gross	4,065,229			3,759,973
Accumulated depreciation	(607,903		)	(444,842		)
Property, plant and equipment, net	$	3,457,326		$	3,315,131

Land in the table above includes $120.2 million and $106.2 million of rights-of-way at December 31, 2018 and 2017, respectively. The weighted average remaining useful life of rights-of-way at December 31, 2018, was approximately 19 years.

We recorded depreciation expense of $173.1 million, $126.3 million and $87.9 million for the years ended December 31, 2018, 2017 and 2016, respectively.

We include within the cost of property, plant and equipment interest costs incurred while an asset is being constructed. We capitalized $12.6 million, $18.4 million and $17.0 million of interest costs during the years ended December 31, 2018, 2017 and 2016, respectively.

Goodwill and Other Intangible Assets

12 Months Ended

Dec. 31, 2018

Goodwill And Other Intangible Assets [Abstract]

Goodwill and Other Intangible Assets

GOODWILL AND OTHER INTANGIBLE ASSETS

Goodwill

Goodwill relates to our U.S Liquids segment. Changes in goodwill balances during the period from December 31, 2015 to December 31, 2018 are shown below (in thousands):



Balance, December 31, 2015	$	48,032
U.S. Gas impairment loss	(13,052		)
Currency translation adjustments	(750		)
Balance, December 31, 2016	34,230
U.S. Liquids - Crude oil trucking impairment loss	(26,628		)
Reclassification of Mexican asphalt business goodwill as held for sale (Note 4)	(7,808		)
U.S. Liquids - HFOTCO acquisition (Note 5)	257,302
Currency translation adjustments	206
Balance, December 31, 2017	257,302
Balance, December 31, 2018	$	257,302

For U.S. federal income tax purposes, goodwill is amortized on a straight-line basis over 15 years.

We assess our goodwill for impairment at least annually as of October 1. Testing goodwill for impairment requires estimation of future economic benefit based on management's judgment and assumptions about numerous variables including selling prices, costs, the level of activity and appropriate discount rates. Future results may be different from management's assumptions. No impairments were indicated as of October 1, 2018.

U.S. Liquids - Crude oil trucking goodwill impairment - 2017

Based on market conditions, in the third-quarter of 2017, management lowered the long range forecast for our crude oil trucking business unit, which provides truck transportation services as part of our U.S. Liquids segment. The decrease in the long range forecast for crude oil trucking is primarily due to the on-going challenging business environment. We viewed the decrease in the forecast as a triggering event that indicated a potential impairment and performed an interim impairment analysis on the business unit’s assets including goodwill and intangible assets.

We performed a recoverability test of our definite lived assets under ASC 360 whereby we compared the undiscounted cash flows of the asset group, which was determined to be the entire crude oil trucking reporting unit and included goodwill, to the carrying value of the assets at September 30, 2017. This test indicated that the assets were not fully recoverable. Therefore, we estimated the fair value of the definite lived assets using an income approach, supplemented by a market approach to measure impairment. We also performed an interim impairment test of our goodwill associated with the crude oil trucking reporting unit and determined the estimated fair value was less than the adjusted carrying value of the reporting unit resulting in impairment of goodwill. The cash flow models used to determine recoverability of our assets and to measure impairment expense involved using significant judgments and assumptions, which included the discount rate, anticipated revenue and volume growth rates, estimated operating expenses and capital expenditures, which were based on our operating and capital budgets as well as our strategic plans. We considered the market approach by comparing the revenue and earnings multiples implied by our income approach to those of comparable companies for reasonableness and for estimating the fair value of certain assets of our reporting unit.

We recorded a $26.6 million impairment of goodwill and a $12.1 million impairment of intangible assets, which are reflected in “loss (gain) on disposal or impairment, net” in our consolidated statements of operations and comprehensive income (loss).

U.S. Gas goodwill impairment - 2016

In March 2016, our U.S. Gas segment revised the volume forecast for its northern Oklahoma system based on revised volume forecasts provided by certain producers who have chosen to adjust plans for production following release of the Oklahoma Corporation Commission’s Regional Earthquake Response Plan that curtails the amount of volume that can be injected into disposal wells.

Based on the reduction to our forecast, we tested our U.S. Gas segment's long-lived assets, finite-lived intangible assets and goodwill for impairment at March 31, 2016. No impairment was indicated for U.S. Gas' long-lived assets and finite-lived intangible assets based on an undiscounted cash flow analysis. However, we did record an impairment of U.S. Gas' goodwill for the entire balance of $13.1 million.

To test the goodwill for impairment, we used an income approach, supplemented by a market approach to calculate the fair value of the reporting unit. Under the income approach, we utilized a discounted cash flow model to determine the fair value of our U.S. Gas operations. Significant judgments and assumptions included the discount rate, anticipated revenue and volume growth rates, estimated operating expenses and capital expenditures, which were based on our operating and capital budgets as well as our strategic plans. A significant underlying assumption is that commodity prices will eventually improve, water disposal issues will be resolved and production volumes will begin to increase. If production does not increase in the future or the production takes longer than anticipated to return, this would negatively affect our key assumptions and potentially lead to finite-lived intangible and long-lived asset impairments in the future. We considered the market approach by comparing the revenue and earnings multiples implied by our income approach to those of comparable companies for reasonableness. See Note 4 for 2017 impairment of long-lived assets.

Other intangible assets

The gross carrying amount and accumulated amortization of intangible assets are shown below (in thousands):



	December 31, 2018							December 31, 2017
	Gross Carrying Amount		Accumulated Amortization			Net Carrying Amount		Gross Carrying Amount		Accumulated Amortization			Net Carrying Amount
Customer relationships	$	424,000	$	(67,917	)	$	356,083	$	424,000	$	(49,717	)	$	374,283
Non-compete agreement	30,000		(21,250		)	8,750		30,000		(6,250		)	23,750
Trade names	52		(47		)	5		52		(42		)	10
Customer contract	1,000		(800		)	200		1,000		(400		)	600
Total other intangible assets	$	455,052	$	(90,014	)	$	365,038	$	455,052	$	(56,409	)	$	398,643

Changes in other intangible asset balances during the period from December 31, 2015 to December 31, 2018, are shown below (in thousands):



Balance, December 31, 2015	$	162,223
Amortization	(10,928		)
Currency translation adjustments	(317		)
Balance, December 31, 2016	150,978
U.S. Liquids - HFOTCO acquisition (Note 5)	291,000
U.S. Liquids - Crude oil trucking impairment	(12,087		)
Reclassification of Mexican asphalt assets as held for sale (Note 4)	(715		)
Amortization	(30,628		)
Currency translation adjustments	95
Balance, December 31, 2017	398,643
Amortization	(33,605		)
Balance, December 31, 2018	$	365,038

Our other intangible assets consist primarily of customer relationships at our U.S. Liquids and U.S. Gas segments and a non-compete agreement at our U.S. Liquids segment. These assets may be subject to impairments in the future if we are unable to maintain the relationships with the customers to which the assets relate or if the cash flows associated with those relationships decrease.

We estimate that future amortization of other intangible assets will be as follows (in thousands):



For the year ending:
December 31, 2019	$	39,455
December 31, 2020	30,000
December 31, 2021	30,200
December 31, 2022	28,600
December 31, 2023	27,100
Thereafter	209,683
Total estimated amortization expense	$	365,038

Financial Instruments and Concentrations of Risk

12 Months Ended

Dec. 31, 2018

Fair Value Disclosures [Abstract]

Financial Instruments and Concentrations of Risk

FINANCIAL INSTRUMENTS AND CONCENTRATIONS OF RISK

Fair value of financial instruments

We record certain financial assets and liabilities at fair value at each balance sheet date. The table below summarizes the balances of commodity derivative assets and liabilities at December 31, 2018 and 2017 (in thousands):



	December 31, 2018
	Level 1			Level 2			Level 3			Netting⁽¹⁾			Total
Assets:
Commodity derivatives ⁽²⁾	$	4,658		$	—		$	—		$	(973	)	$	3,685
Total assets	4,658			—			—			(973		)	3,685
Liabilities:
Commodity derivatives	973			—			—			(973		)	—
Foreign currency forwards	—			2,985			—			—			2,985
Interest rate swaps	—			—			1,482			—			1,482
Total liabilities	973			2,985			1,482			(973		)	4,467
Net assets (liabilities) at fair value	$	3,685		$	(2,985	)	$	(1,482	)	$	—		$	(782	)

	December 31, 2017
	Level 1			Level 2			Level 3			Netting⁽¹⁾			Total
Assets:
Commodity derivatives ⁽²⁾	$	602		$	—		$	—		$	(602	)	$	—
Foreign currency forwards	—			2,564			—			—			$	2,564
Total assets	602			2,564			—			(602		)	2,564
Liabilities:
Commodity derivatives	1,970			—			—			(602		)	1,368
Interest rate swaps	—			—			1,228			—			1,228
Total liabilities	1,970			—			1,228			(602		)	2,596
Net assets (liabilities) at fair value	$	(1,368	)	$	2,564		$	(1,228	)	$	—		$	(32	)



(1)	Relates primarily to exchange traded futures. Gain and loss positions on multiple contracts are settled net on a daily basis with the exchange.
(2)	Commodity derivatives are subject to netting arrangements.

“Level 1” measurements are based on inputs consisting of unadjusted quoted prices in active markets that are accessible at the measurement date for identical, unrestricted assets or liabilities. These include commodity futures contracts that are traded on an exchange.

“Level 2” measurements are based on inputs consisting of market observable and corroborated prices for similar derivative contracts. Assets and liabilities classified as Level 2 include over the counter (“OTC”) traded physical fixed priced purchases and sales forward contracts.

“Level 3” measurements are based on inputs from a pricing service and/or internal valuation models incorporating observable and unobservable market data. These could include commodity derivatives, such as forwards and swaps for which there is not a highly liquid market and therefore are not included in Level 2 above and interest rate swaps for which certain unobservable inputs are used in the valuation.

Financial assets and liabilities are classified based on the lowest level of input that is significant to the fair value measurement. Our assessment of the significance of a particular input to the measurement requires judgment and may affect the valuation of assets and liabilities and their placement within the fair value levels. At December 31, 2018, all of our physical fixed price forward purchases and sales contracts were being accounted for as normal purchases and normal sales.

Our assessment of the significance of a particular input to the measurement requires judgment, and may affect the valuation of assets and liabilities and their placement within the fair value levels. The following table summarizes changes in the fair value of our net financial liabilities classified as Level 3 in the fair value hierarchy (in thousands):



	Year Ended December 31, 2018		Year Ended December 31, 2017
Net liabilities - beginning balance	$	1,228	$	—
Interest rate swaps acquired through acquisition (Note 5)	—		3,275
Transfers out of Level 3	—		—
Realized/Unrealized (gain) loss included in earnings*	163		(1,124		)
Settlements	91		(923		)
Net liabilities - ending balance	$	1,482	$	1,228

*Gains and losses related to interest rate swaps are recorded in interest expense in the condensed consolidated statements of operations and comprehensive income (loss).

There were no financial assets or liabilities classified as Level 3 during the year ended December 31, 2016.

See Note 12 for fair value of debt instruments and Note 13 for fair value of benefit plan assets. The approximate fair value of cash and cash equivalents, accounts receivable and accounts payable is equal to book value due to the short-term nature of these items.

Commodity derivative contracts

Our consolidated results of operations and cash flows are impacted by changes in market prices for petroleum products. This exposure to commodity price risk is managed, in part, by entering into various commodity derivatives.

We seek to manage the price risk associated with our marketing operations by limiting our net open positions through (i) the concurrent purchase and sale of like quantities of petroleum products to create back-to-back transactions that are intended to lock in positive margins based on the timing, location or quality of the petroleum products purchased and delivered or (ii) derivative contracts. Our storage and transportation assets can also be used to mitigate time and location basis risks, respectively. All marketing activities are subject to our Comprehensive Risk Management Policy, a Delegation of Authority policy and their supporting policies and procedures, which establish limits in order to manage risk and mitigate financial exposure.

Our commodity derivatives can be comprised of swaps, futures contracts and forward contracts of crude oil, natural gas and natural gas liquids. These are defined as follows:

Swaps – OTC transactions where a floating price, basis or index is exchanged for a fixed (or a different floating) price, basis or index at a preset schedule in the future, according to an agreed-upon formula.

Futures contracts – Exchange traded contracts to buy or sell a commodity. These contracts are standardized by the exchange in terms of quality, quantity, delivery period and location for each commodity.

Forward contracts – OTC contracts to buy or sell a commodity at an agreed upon future date. The buyer and seller agree on specific terms (price, quantity, delivery period and location) and conditions at the inception of the contract.

The following table sets forth the notional quantities for derivative instruments entered into (in thousands of barrels):



	Year Ended December 31,
	2018	2017	2016
Sales	14,013	12,979	33,694
Purchases	13,417	13,430	33,819

We have not designated any of our commodity derivative instruments as accounting hedges. We have recorded the fair value of our commodity derivative instruments on our consolidated balance sheets in "other current assets" and "other current liabilities" in the following amounts (in thousands):



December 31, 2018				December 31, 2017
Other Current Assets		Other Current Liabilities		Other Current Assets		Other Current Liabilities
$	3,685	$	—	$	—	$	1,368

We have posted margin deposits as collateral with brokers who have the right of set off associated with these funds. Our margin deposit balances were $0.1 million and $1.9 million at December 31, 2018 and 2017, respectively. These margin account balances have not been offset against our net commodity derivative instrument (contract) positions. Had these margin account balances been netted against our net commodity derivative instrument (contract) positions as of December 31, 2018 and 2017, we would have had net asset positions of $3.8 million and $0.5 million, respectively.

Realized and unrealized gains (losses) from our commodity derivatives were recorded to product revenue in the following amounts (in thousands):



	Year Ended December 31,
	2018		2017			2016
Realized and unrealized gain (loss)	$	12,088	$	(2,193	)	$	(4,485	)

Interest rate swaps

We have interest rate swaps which allow us to limit exposure to interest rate fluctuations. The swaps only apply to a portion of our outstanding debt and provide only partial mitigation of interest rate fluctuations. We have not designated the swaps as hedges, as such changes in the fair value of the swaps are recorded through current period earnings as a component of interest expense. At December 31, 2018 and 2017, we had interest rate swaps with notional values of $524.3 million and $491.1 million, respectively. At December 31, 2018 and 2017, the fair value of our interest rate swaps was $1.5 million and $1.2 million, respectively, which was reported within "other current liabilities" and "other noncurrent liabilities” in our condensed consolidated balance sheet. For the year ended December 31, 2018, we recognized realized and unrealized losses of $0.2 million related to interest rate swaps. For the year ended December 31, 2017, we recognized realized and unrealized gains of $1.1 million related to interest rate swaps. We did not have any interest rate swaps during the year ended December 31, 2016.

Foreign currency forwards

We have foreign currency forwards primarily to purchase Canadian dollars to limit exposure to foreign currency rate fluctuations for capital contributions to our Canadian operations. We have not designated the forwards as hedges, as such changes in the fair value of the forwards are recorded through current period earnings as a component of foreign currency translation gain/loss. At December 31, 2018 and 2017, we had foreign currency forwards with notional values of $56.1 million and $197.7 million, respectively. At December 31, 2018 and 2017, the fair value of our foreign currency swaps was $3.0 million and $2.6 million, respectively, which is reported within "other current liabilities" and "other noncurrent assets, net", respectively, in our consolidated balance sheet. For the year ended December 31, 2018, we recognized realized and unrealized losses of $10.2 million, related to foreign currency forwards. For the year ended December 31, 2017, we recognized realized and unrealized gains of $2.8 million, related to foreign currency forwards. We did not have any foreign currency forwards during the year ended December 31, 2016.

Concentrations of risk

During the year ended December 31, 2018, one customer, primarily of our U.S. Liquids segment, accounted for more than 10% of our consolidated revenue with revenues of $645.0 million. One third-party supplier, primarily of our U.S. Liquids segment, accounted for more than 10% of our costs of products sold with purchases of $248.7 million. At December 31, 2018, two customers, primarily of our U.S. Liquids segment, accounted for approximately 28% of our consolidated accounts receivable.

Our U.S. Gas segment has a significant concentration of producers which account for a large portion of our U.S. Gas segment's volumes. During the year ended December 31, 2018, three producers accounted for approximately 89% of our total processed volumes. During the year ended December 31, 2018, two producers accounted for 83% of our total

gathered volumes. Additionally, all of the processing and gathering volumes from these customers are produced in the Northern Oklahoma region.

Our Canada segment's processing plants require a minimum rate of sulfur tonnage to operate, and to comply with the regulatory requirements for air emissions. We have several large producers that provide significant sour gas to our plants. If these producers shut in their sour gas production due to low commodity prices, it could result in regulatory non-compliance, as well as operating and financial impacts to our Canada segment.

Assets and liabilities of subsidiaries outside the United States

The following table summarizes the assets and liabilities (excluding affiliate balances) at December 31, 2018, of our subsidiaries outside the United States (in thousands):



	Canada
Cash and cash equivalents	$	17,107
Other current assets	78,542
Noncurrent assets	590,714
Total assets	$	686,363

Current liabilities	$	69,798
Noncurrent liabilities	76,192
Total liabilities	145,990
Net assets	$	540,373

Employees

At December 31, 2018, we had approximately 880 employees, including approximately 265 employees in Canada. Approximately 55 of the employees in Canada are represented by labor unions and are subject to collective bargaining agreements governing their employment with us. This collective agreement expires on January 31, 2019. We have never had a labor related work stoppage and believe our employee relations are good.

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Income Taxes

12 Months Ended

Dec. 31, 2018

Income Tax Disclosure [Abstract]

Income Taxes

INCOME TAXES

Income tax expense (benefit)

Our consolidated income from continuing operations before income taxes was generated in the following jurisdictions (in thousands):



	Year Ended December 31,
	2018			2017			2016
U.S.	$	(53,517	)	$	(64,423	)	$	(766	)
Foreign	52,493			44,885			25,297
Consolidated	$	(1,024	)	$	(19,538	)	$	24,531

The following table summarizes income tax provision (benefit) from continuing operations by jurisdiction (in thousands):



	Year Ended December 31,
	2018			2017			2016
Current income tax provision:
Foreign	$	14,343		$	7,058		$	2,821
U.S. federal	—			—			—
U.S. state	650			383			—
	14,993			7,441			2,821
Deferred income tax provision (benefit):
Foreign	9,610			5,318			4,071
U.S. federal	(664		)	(15,379		)	5,142
U.S. state	(635		)	232			(766		)
	8,311			(9,829		)	8,447
Provision (benefit) for income taxes	$	23,304		$	(2,388	)	$	11,268

The following table reconciles income tax provision at the U.S. federal statutory rate to the consolidated provision (benefit) for income taxes (in thousands):



	Year Ended December 31,
	2018				2017			2016
Income from continuing operations before income taxes	$	(1,024	)		$	(19,538	)	$	24,531
U.S. federal statutory rate	21		%		35		%	35		%
Provision at statutory rate	(215		)		(6,838		)	8,586
State income taxes—net of federal benefit	13				401			(498		)
Effect of rates other than statutory	3,042				(3,842		)	(1,966		)
Effect of U.S. taxation on foreign branches	11,023				15,710			8,854
Noncontrolling interest	(508		)		—			(3,908		)
Foreign tax credit and offset to branch deferreds	1,447				45,245			(6,026		)
Effect of U.S. deduction of foreign tax	(3,012		)		(7,514		)	—
Impact of valuation allowance on deferred tax assets	—				(65,327		)	6,026
Foreign withholding taxes	10,187				858			18
Stock-based compensation	1,427				1,351			—
Effect of U.S. federal statutory rate reduction	—			—	17,638			—
Other, net	(100		)		(70		)	182
Provision (benefit) for income taxes	$	23,304			$	(2,388	)	$	11,268

For the years ended December 31, 2018, 2017 and 2016, the foreign subsidiaries are disregarded entities for U.S. federal income tax purposes. The foreign earnings are taxed in foreign jurisdictions as well as in the U.S. Foreign tax credits, subject to limitations, or foreign tax deductions are available to reduce U.S. taxes. The decision to deduct foreign taxes or claim the foreign tax credit is made with respect to each tax period.

Deferred tax positions

Deferred income taxes reflect the effects of temporary differences between the amounts of assets and liabilities recognized for financial reporting purposes and the amounts recognized for income tax purposes. Significant components of deferred tax assets and liabilities are as follows at December 31, 2018 and 2017 (in thousands):



	December 31,
	2018				2017



Deferred tax assets:
Net operating loss and other credit carryforwards	$	139,274		$	44,867
Compensation and benefits	5,480			7,156
Inventories	44			322
Intangible assets	—			16,714
Pension plan	813			1,760
Allowance for doubtful accounts	577			956
Deferred revenue	2,493			4,953
Foreign tax credit and offset to branch deferreds	55,272			56,719
Other	19,127			28,201
less: valuation allowance	(45,614		)	(45,682		)
Net deferred tax assets	177,466			115,966
Deferred tax liabilities:
Intangible assets	(12,849		)	(5,074		)
Prepaid expenses	—			(1,447		)
Property, plant and equipment	(189,529		)	(108,646		)
Equity investment in partnerships	(3,572		)	(24,315		)
Other	(2,010		)	(2,402		)
Total deferred tax liabilities	(207,960		)	(141,884		)
Net deferred tax liabilities	$	(30,494	)	$	(25,918	)

At December 31, 2018, we had a cumulative U.S. federal net operating loss of approximately $535.6 million that can be carried forward to apply against taxable income generated in future years. $350.4 million of this carryforward may be carried forward indefinitely and the remaining carryforward begins to expire in 2031. We had cumulative U.S. state net operating losses of approximately $371.0 million available for carryforward, which begin to expire in 2019. We had foreign net operating losses of $0.8 million available for carryforward, which begin to expire in 2025. We had foreign tax credits of approximately $44.6 million available for carryforward, which begin to expire in 2020. We had interest expense limitation of $31.8 million available for indefinite carryforward.

The valuation allowance decreased by $0.1 million during 2018. The change is primarily related to state net operating losses.

We have a valuation allowance on a small portion of our state net operating loss carryovers with shorter carryover periods, our foreign net operating loss carryovers and our foreign tax credit carryover. We have not released the valuation allowance on the foreign tax credits due to the foreign tax credit limitation and the relative subjectivity of forecasts of the relational magnitude of U.S. and foreign taxable income in future periods, as well as the shorter carryover period available for the credits. Deferred tax assets are reduced by a valuation allowance when a determination is made that it is more likely than not that some, or all, of the deferred tax assets will not be realized based on the weight of all available evidence. Evidence which is objectively verifiable carries a higher weight in the analysis. The ultimate realization of deferred tax assets is dependent upon the existence of sufficient taxable income of the appropriate character within the carryback and carryforward period available under the tax law. Sources of taxable income include future reversals of existing taxable temporary differences, future earnings and available tax planning strategies.

We have analyzed filing positions in all of the federal, state and foreign jurisdictions where we are required to file income tax returns and determined that no accruals related to uncertainty in tax positions are required. All income tax years of the Company ending after the emergence from bankruptcy remain open for examination in U.S. jurisdictions under general operation of the statute of limitations, including special provisions with regard to net operating loss carryovers. In foreign jurisdictions, all tax periods prior to the emergence from bankruptcy are closed. The statute of limitations has not been waived with respect to any foreign jurisdictions post emergence and tax periods are open for

examination in accordance with the general statutes of each foreign jurisdiction. Currently, there are no examinations in progress for our federal, state or foreign jurisdictions.

Long-Term Debt

12 Months Ended

Dec. 31, 2018

Debt Disclosure [Abstract]

Long-Term Debt

LONG-TERM DEBT

Our long-term debt consisted of the following (dollars in thousands):



	Interest rate at December 31, 2018	December 31, 2018			December 31, 2017
Senior unsecured notes due 2022	5.625%	400,000			400,000
Senior unsecured notes due 2023	5.625%	350,000			350,000
Senior unsecured notes due 2025	6.375%	325,000			325,000
Senior unsecured notes due 2026	7.250%	300,000			300,000
SemGroup $1.0 billion corporate revolving credit facility⁽¹⁾
Alternate base rate borrowings	7.250%	24,500			—
Eurodollar borrowings	5.156%	95,000			131,000
HFOTCO acquisition final payment		—			565,868
HFOTCO term loan B ⁽²⁾	5.280%	597,000			532,125
HFOTCO tax exempt notes payable due 2050	3.399%	225,000			225,000
HFOTCO $75 million revolving credit facility		—			60,000
Capital leases		—			25
Unamortized premium (discount) and debt issuance costs, net		(31,666		)	(30,398		)
Total long-term debt, net		2,284,834			2,858,620
Less: current portion of long-term debt		6,000			5,525
Noncurrent portion of long-term debt, net		$	2,278,834		$	2,853,095


(1)	SemGroup $1.0 billion corporate revolving credit facility matures on May 15, 2021.


(2)	HFOTCO term loan B is due in quarterly installments of $1.5 million, with a final payment due on June 26, 2025.

HFOTCO credit agreement

On June 26, 2018, HFOTCO and Buffalo Gulf Coast Terminals LLC ("BGCT") entered into an Amendment and Restatement Agreement (the “Amendment and Restatement Agreement”). Pursuant to the Amendment and Restatement Agreement, the HFOTCO credit agreement was amended and restated in its entirety (as so amended and restated, the “Restated HFOTCO Credit Agreement”).

The Restated HFOTCO Credit Agreement increased the aggregate term loans incurred thereunder to $600 million, terminated the HFOTCO $75.0 million revolving credit facility, and extended the maturity date of the term loans to June 26, 2025 (the “Maturity Date”). In addition, HFOTCO may incur additional term loans in an aggregate amount not to exceed the greater of $120 million and a measure of HFOTCO’s EBITDA, defined in the credit agreement, at the time of determination, plus additional amounts subject to satisfaction of certain leverage-based criteria, subject to receiving commitments for such additional term loans from either new lenders or increased commitments from existing lenders. The term loan B was issued at a discount of $1.5 million.

At HFOTCO’s option, the term loans will bear interest at the Eurodollar rate or an alternate base rate (“ABR”), plus, in each case, an applicable margin of 2.75% relating to any term loans accruing interest at the Eurodollar rate and 1.75% relating to term loans accruing interest at ABR.

HFOTCO acquisition final payment

On April 17, 2018, we made the final payment related to the HFOTCO acquisition in the amount of $579.6 million. The payment was funded through revolving credit facility borrowings and cash on hand.

Early extinguishment of senior unsecured notes due 2021

On March 15, 2017, we purchased $290 million of our outstanding $300 million, 7.50% senior unsecured notes due 2021 (the “2021 Notes”) through a tender offer. The purchase price included a premium and interest to the purchase date. On March 17, 2017, a notice of redemption was issued for the remaining $10 million of the 2021 Notes which were not purchased through the tender offer pursuant to the redemption and satisfaction and discharge provisions of the indenture governing the 2021 Notes. These remaining 2021 Notes were redeemed on June 15, 2017, including a redemption premium and accrued unpaid interest to the redemption date. We recorded a loss on early extinguishment of $19.9 million for the above transactions, which included premiums totaling $15.9 million and the write off of $3.6 million of associated unamortized debt issuance costs.

Issuance of senior unsecured notes due 2025 and 2026

On March 15, 2017, we sold $325 million of 6.375% senior unsecured notes due 2025 (the “2025 Notes”). The 2025 Notes were sold at 98.467% of par, a discount of $5.0 million. The discount is reported as a reduction to the face value of the 2025 Notes on our condensed consolidated balance sheets and is being amortized over the life of the 2025 Notes using the interest method.

The net proceeds from the offering of $315.1 million, after the discount and $4.9 million of initial purchasers’ fees and offering expenses, together with cash on hand, were used to purchase and redeem the 2021 Notes.

On September 20, 2017, we sold $300 million of 7.25% senior unsecured notes due 2026 (the “2026 Notes”). The 2026 Notes were sold at 98.453% of par, a discount of $4.6 million. The discount is reported as a reduction to the face value of the 2026 Notes on our condensed consolidated balance sheets and is being amortized over the life of the 2026 Notes using the interest method.

The net proceeds from the offering of $290.3 million, after the discount and $5.1 million of initial purchasers’ fees and offering expenses, were used to repay amounts borrowed under our revolving credit facility.

Senior unsecured notes

Our senior unsecured notes (collectively, the "Notes") are guaranteed by certain of our subsidiaries: Rose Rock Finance Corporation, Rose Rock Midstream Operating, LLC, Rose Rock Midstream Energy GP, LLC, Rose Rock Midstream Crude, L.P., Rose Rock Midstream Field Services, LLC, SemGas, L.P., SemMaterials, L.P., SemGroup Europe Holding, L.L.C., SemOperating G.P., L.L.C., SemMexico, L.L.C., SemDevelopment, L.L.C., Mid-America Midstream Gas Services, L.L.C., SemCrude Pipeline, L.L.C., Wattenberg Holding, LLC, LLC, Beachhead Holdings LCC, Beachhead I LLC and Beachhead II LLC (collectively, the "Guarantors"). The guarantees of the Notes are full and unconditional and constitute the joint and several obligations of the Guarantors.

The Notes are governed by indentures, as supplemented, between the Company and its subsidiary Guarantors and Wilmington Trust, N.A., as trustee (the “Indentures”). The Indentures include customary covenants, including limitations on our ability to incur additional indebtedness or issue certain preferred shares; pay dividends and make certain distributions, investments and other restricted payments; create certain liens; sell assets; enter into transactions with affiliates; enter into sale and lease-back transactions; merge, consolidate, sell or otherwise dispose of all or substantially all of our assets; and designate our subsidiaries as unrestricted under the Indentures.

The Indentures include customary events of default, including events of default relating to non-payment of principal and other amounts owing from time to time, failure to provide required reports, failure to comply with agreements in the Indentures, cross payment-defaults to any material indebtedness, bankruptcy and insolvency events, certain unsatisfied judgments, and invalidation or cessation of the subsidiary guarantee of a significant subsidiary. A default would permit holders to declare the Notes and accrued interest due and payable.

The Notes are effectively subordinated in right of payment to any of our, and the Guarantors', existing and future secured indebtedness to the extent of the value of the collateral securing such indebtedness and are structurally subordinated to the obligations of any subsidiary that is not a guarantor of the Notes.

The Company may issue additional Notes under the Indentures from time to time, subject to the terms of the Indentures.

Except as described below, the Company may redeem the Notes, in whole or in part, at the redemption prices (expressed as percentages of principal amount) set forth below, plus accrued and unpaid interest, if redeemed during the twelve-month period beginning with each period as indicated below:



2022 Notes
From and after July 15, 2018		102.813%
From and after July 15, 2019		101.406%
From and after July 15, 2020		100.000%



2023 Notes
Not redeemable before May 15, 2019
From and after May 15, 2019		102.813%
From and after May 15, 2020		101.406%
From and after May 15, 2021		100.000%



2025 Notes
Not redeemable before March 15, 2020
From and after March 15, 2020		103.188%
From and after March 15, 2021		101.594%
From and after March 15, 2022		100.000%



2026 Notes
Not redeemable before March 15, 2021
From and after March 15, 2021		103.625%
From and after March 15, 2022		101.813%
From and after March 15, 2023		100.000%

Prior to the redemption dates set forth above, the Company may, at its option, on one or more occasions, redeem up to 35% of the sum of the original aggregate principal amount of the Notes at a redemption price equal to the aggregate principal amount thereof plus a premium equal to stated interest rate of the Notes, plus accrued and unpaid interest, with the net cash proceeds of one or more equity offerings of the Company, subject to certain conditions.

Prior to the redemption dates set forth above, the Company may also redeem all or part of the Notes at a price equal to the principal plus a premium equal to the greater of 1% of the principal or the excess of the present value of the first redemption price from the table above plus all required interest payments due through the first redemption date in the table above, computed using a discount rate based on a published United States Treasury Rate plus 50 basis points, over the principal value of such Note.

In the event of a change of control, the Company is required to offer to repurchase the Notes at an amount equal to 101% of the principal plus accrued and unpaid interest.

Pledges and guarantees

Our senior unsecured notes are guaranteed by certain subsidiaries. See Note 25 for additional information.

Our $1.0 billion corporate revolving credit facility is guaranteed by all of SemGroup’s material domestic subsidiaries, with the exception of Maurepas Pipeline LLC and HFOTCO, and secured by a lien on substantially all of the property and assets of SemGroup Corporation and the other loan parties, subject to customary exceptions.

The HFOTCO term loan B and HFOTCO tax exempt notes payable are secured by substantially all of the assets of HFOTCO and its immediate parent, Buffalo Gulf Coast Terminals LLC. The HFOTCO tax exempt notes payable have a priority position over the HFOTCO term loan B.

Covenants and restrictions

The SemGroup credit agreement includes customary affirmative and negative covenants, including limitations on the creation of new indebtedness, liens, sale and lease-back transactions, new investments, making fundamental changes including mergers and consolidations, making of dividends and other distributions, making material changes in our business, modifying certain documents and maintenance of a consolidated leverage ratio and an interest coverage ratio. In addition, the credit agreement prohibits any commodity transactions that are not permitted by our Risk Governance Policies.

The terms of the SemGroup credit facility restrict, to some extent, the payment of cash dividends on our common stock.

The Restated HFOTCO Credit Agreement includes customary representations and warranties and affirmative and negative covenants, which were made only for the purposes of the Restated HFOTCO Credit Agreement and as of the specific date (or dates) set forth therein, and may be subject to certain limitations as agreed upon by the contracting parties, and apply only to BGCT, HFOTCO and any subsidiaries of HFOTCO party to the Restated HFOTCO Credit Agreement. Such limitations include the creation of new liens, indebtedness, making of certain restricted payments and payments on indebtedness, making certain dispositions, making material changes in business activities, making fundamental changes including liquidations, mergers or consolidations, making certain investments, entering into certain transactions with affiliates, making amendments to material agreements, modifying the fiscal year, dealing with hazardous materials in certain ways, entering into certain hedging arrangements, entering into certain restrictive agreements, and funding or engaging in sanctioned activities.

The Restated HFOTCO Credit Agreement includes customary events of default, including events of default relating to inaccuracy of representations and warranties in any material respect when made or when deemed made, non-payment of principal and other amounts owing under the Restated HFOTCO Credit Agreement, including, in respect of, violation of covenants, cross acceleration to any material indebtedness of BGCT, HFOTCO and its subsidiaries, bankruptcy and insolvency events, certain unsatisfied judgments, certain ERISA events, certain invalidities of loan documents and the occurrence of a change of control. A default under the Restated HFOTCO Credit Agreement would permit the participating banks to require immediate repayment of any outstanding loans with interest and any unpaid accrued fees, and subject to intercreditor arrangements with the holders of the HFOTCO tax exempt notes payable, exercise other rights and remedies.

The indentures covering HFOTCO's tax exempt notes payable due 2050 ("IKE Bonds") are subject to the Continuing Covenant Agreement. The Continuing Covenant Agreement includes customary representations and warranties and affirmative and negative covenants, which were made only for the purposes of the Continuing Covenant Agreement and as of the specific date (or dates) set forth therein, may be subject to certain limitations as agreed upon by the contracting parties, and apply only to BGCT, HFOTCO and any subsidiaries of HFOTCO party to the Continuing Covenant Agreement. Such covenants include limitations on the creation of new liens, indebtedness, making of certain restricted payments and payments on indebtedness, making certain dispositions, making material changes in business activities, making fundamental changes including liquidations, mergers or consolidations, making certain investments, entering into certain transactions with affiliates, making amendments to certain credit or organizational agreements, modifying the fiscal year, creating or dealing with hazardous materials in certain ways, entering into certain hedging arrangements, entering into certain restrictive agreements, funding or engaging in sanctioned activities, taking actions or causing the trustee to take actions that materially adversely affect the rights, interests, remedies or security of the bondholders, taking actions to remove the trustee, making certain amendments to the bond documents, and taking actions or omitting to take actions that adversely impact the tax-exempt status of the IKE Bonds.

In addition, the Continuing Covenant Agreement contains financial performance covenants as follows:


•	the super senior leverage ratio of BGCT and its restricted subsidiaries under the Continuing Covenant Agreement may not exceed 3.50 to 1.00 as of the last day of any fiscal quarter; and


•	the interest coverage ratio of BGCT and its restricted subsidiaries under the Continuing Covenant Agreement may not be less than 2.00 to 1.00 as of the last day of any fiscal quarter.

See "senior unsecured notes" section above for discussion of covenants and restrictions related to the Notes.

Letters of credit

We had the following outstanding letters of credit at December 31, 2018 (dollars in thousands):



SemGroup $1.0 billion revolving credit facility	2.75%	$	24,335
Secured bi-lateral⁽¹⁾	1.75%	$	19,053

(1) Secured bi-lateral letters of credit are external to the SemGroup $1.0 billion revolving credit facility and do not reduce availability for borrowing on the credit facility.

Scheduled principal payments

The following table summarizes the scheduled principal payments as of December 31, 2018 (in thousands):



	Total
For the year ended:
December 31, 2019	$	6,000
December 31, 2020	6,000
December 31, 2021	125,500
December 31, 2022	406,000
December 31, 2023	356,000
Thereafter	1,417,000
Total	$	2,316,500

Fair value

We estimate the fair value of the Notes based on unadjusted, transacted market prices near the measurement date. Our other long-term debts are estimated to be carried at fair value as a result of the recent timing of borrowings or acquisition. We estimate the fair value of our consolidated long-term debt, including current maturities, to be approximately $2.2 billion at December 31, 2018, which is categorized as a Level 2.

Employee Benefit Plans

12 Months Ended

Dec. 31, 2018

Retirement Benefits [Abstract]

Employee Benefit Plans

EMPLOYEE BENEFIT PLANS

Defined contribution plans

We sponsor defined contribution retirement plans in which the majority of employees are eligible to participate. Our contributions to the defined contribution plans were $3.0 million, $3.0 million, and $2.7 million for the years ended December 31, 2018, 2017 and 2016, respectively.

Pension plans

We sponsor a defined benefit pension plan and a supplemental defined benefit pension plan for certain employees of the Canada segment hired before June 30, 2001 (the “Canada Plans”). Additionally, we sponsor a defined benefit pension plan for certain employees of the U.S. Liquids segment at HFOTCO and a supplemental defined benefit plan covering a former key executive of HFOTCO (the “HFOTCO Plans”). These plans are closed to new participants and do not accrue any additional benefits (collectively, the "Pension Plans").

We recognize the funded status of the Pension Plans, measured as the difference between the fair value of the plan assets and the projected benefit obligation, in the consolidated balance sheets. The table below summarizes the balances of the projected benefit obligation and fair value of the plan assets at December 31, 2018 and 2017 (in thousands):



	December 31,
	2018			2017
Projected benefit obligation	$	50,049		$	53,489
Fair value of plan assets	39,197			43,098
Funded status:	$	(10,852	)	$	(10,391	)

We recorded other noncurrent liabilities of $2.0 million and $2.3 million at December 31, 2018 and 2017, respectively, to reflect the funded status of the Canada Plans.

We recorded other noncurrent liabilities of $8.8 million and $8.1 million at December 31, 2018 and 2017, respectively, to reflect the funded status of the HFOTCO Plans.

All of the Canada Plans' assets are invested in pooled funds that hold highly-liquid securities and are classified as Level 2 within the fair value hierarchy. Substantially all of the HFOTCO Plans' assets are invested in mutual funds, for which the fair values are determined by quoted prices in active markets, and are classified as Level 1 within the fair value hierarchy. The following information discloses the fair values of our Pension Plans' assets, by asset category, for the periods indicated (in thousands):



	December 31, 2018								December 31, 2017
	Level 1		Level 2		Level 3		Total		Level 1		Level 2		Level 3		Total
Cash and cash equivalents	$	831	$	—	$	—	$	831	$	538	$	—	$	—	$	538
Mutual funds	15,125		—		—		15,125		16,671		—		—		16,671
Pooled mutual funds	—		23,241		—		23,241		—		25,889		—		25,889
Total	$	15,956	$	23,241	$	—	$	39,197	$	17,209	$	25,889	$	—	$	43,098

We record changes in the funded status of the Pension Plans to other comprehensive income (loss), net of income taxes. These amounts were losses of $2.6 million, $0.3 million and $1.1 million for the years ended December 31, 2018, 2017 and 2016, respectively.

Retiree medical plan

We sponsor an unfunded, post-employment health benefit plan (the “Health Plan”) for certain employees of our Canada segment. The projected benefit obligation related to the Health Plan was $1.5 million at December 31, 2018, and $1.7 million at December 31, 2017, and is reported within "other noncurrent liabilities" on the consolidated balance sheets.

Commitments and Contingencies

12 Months Ended

Dec. 31, 2018

Commitments and Contingencies Disclosure [Abstract]

Commitments and Contingencies

COMMITMENTS AND CONTINGENCIES

Environmental

We may, from time to time, experience leaks of petroleum products from our facilities and, as a result of which, we may incur remediation obligations or property damage claims. In addition, we are subject to numerous environmental regulations. Failure to comply with these regulations could result in the assessment of fines or penalties by regulatory authorities.

The Kansas Department of Health and Environment ("the KDHE") initiated discussions during our bankruptcy proceeding regarding six of our sites in Kansas (five owned by our U.S. Liquids segment and one owned by our U.S. Gas segment) that KDHE believed, based on their historical use, may have had soil or groundwater contamination in excess of state standards. KDHE sought our agreement to undertake assessments of these sites to determine whether they are contaminated. We reached an agreement with KDHE on this matter and entered into a Consent Agreement and Final Order with KDHE to conduct environmental assessments on the sites and to pay KDHE’s costs associated with their oversight of this matter. We have conducted Phase II investigations at all sites. Four sites are in various stages of follow up investigation, remediation, monitoring, or closure under KDHE oversight. The environmental work at these sites is

being completed under consent orders between Rose Rock Midstream Crude, L.P. and the KDHE. Two of the remaining sites have limited impacts to shallow soil and groundwater and the groundwater is currently being monitored on a semi-annual basis until such time that closure can be granted by the KDHE. No active remediation is anticipated for these two sites. The final two sites have required additional investigation and soil and groundwater remediation may be necessary to achieve KDHE closure. We do not anticipate any penalties or fines for these historical sites.

Other matters

We are party to various other claims, legal actions, and complaints arising in the ordinary course of business. In the opinion of our management, the ultimate resolution of these claims, legal actions, and complaints, after consideration of amounts accrued, insurance coverage, and other arrangements, will not have a material adverse effect on our consolidated financial position, results of operations or cash flows. However, the outcome of such matters is inherently uncertain, and estimates of our consolidated liabilities may change materially as circumstances develop.

Asset retirement obligations

We will be required to incur significant removal and restoration costs when we retire our natural gas gathering and processing facilities in Canada. We have recorded a liability associated with these obligations, which is reported within other noncurrent liabilities on the consolidated balance sheets. The following table summarizes the changes in this liability from December 31, 2015 through December 31, 2018 (in thousands):



Balance, December 31, 2015	$	15,946
Accretion	2,292
Payments made	(159		)
Currency translation adjustments	469
Balance, December 31, 2016	18,548
Accretion	2,812
Payments made	(160		)
Currency translation adjustments	1,404
Balance, December 31, 2017	22,604
Accretion	4,070
Payments made	(3,111		)
Currency translation adjustments	(1,820		)
Balance, December 31, 2018	$	21,743

The December 31, 2018 liability was calculated using the $127.1 million cost we estimate we would incur to retire these facilities, discounted based on our risk-adjusted cost of borrowing and the estimated timing of remediation. An additional $18.1 million of estimated costs are attributable to third-party owners’ proportionate share of the obligations. If an owner fails to perform on its obligations, the other owners (including SemGroup) could be obligated to bear that party’s share of the remediation costs.

The calculation of the liability for an asset retirement obligation requires the use of significant estimates, including those related to the length of time before the assets will be retired, cost inflation over the assumed life of the assets, actual remediation activities to be required and the rate at which such obligations should be discounted. Future changes in these estimates could result in material changes in the value of the recorded liability. In addition, future changes in laws or regulations could require us to record additional asset retirement obligations.

Our other segments may also be subject to removal and restoration costs upon retirement of their facilities. However, we are unable to predict when, or if, our pipelines, storage tanks and other facilities would become completely obsolete and require decommissioning. Accordingly, we have not recorded a liability or corresponding asset, as both the amount and timing of such potential future costs are indeterminable.

Operating leases

We have entered into operating lease agreements for office space, office equipment, land and vehicles. Future minimum payments required under operating leases that have initial or remaining non-cancellable lease terms in excess of one year at December 31, 2018, are as follows (in thousands):



For year ending:
December 31, 2019	$	5,795
December 31, 2020	5,796
December 31, 2021	5,312
December 31, 2022	3,455
December 31, 2023	2,453
Thereafter	40,551
Total future minimum lease payments	$	63,362

We recorded lease and rental expenses of $15.1 million, $15.4 million and $15.0 million for the years ended December 31, 2018, 2017 and 2016, respectively.

Purchase and sale commitments

We routinely enter into agreements to purchase and sell petroleum products at specified future dates. We account for these commitments as normal purchases and sales, therefore, we do not record assets or liabilities related to these agreements until the product is purchased or sold. At December 31, 2018, such commitments included the following (in thousands):



	Volume (barrels)	Value
Fixed price purchases	4,626	$	230,562
Fixed price sales	4,920	$	246,755
Floating price purchases	14,638	$	750,711
Floating price sales	17,290	$	830,407

Certain of the commitments shown in the table above relate to agreements to purchase product from a counterparty and to sell a similar amount of product (in a different location) to the same counterparty. Many of the commitments shown in the table above are cancellable by either party, as long as notice is given within the time frame specified in the agreement (generally 30 to 120 days).

Our U.S. Gas segment has a take or pay contractual obligation related to the fractionation of natural gas liquids through June 2023. At December 31, 2018, the approximate amount of future obligations is as follows (in thousands):



For year ending:
December 31, 2019	$	9,783
December 31, 2020	9,063
December 31, 2021	7,337
December 31, 2022	6,905
December 31, 2023	2,854
Thereafter	—
Total expected future payments	$	35,942

The U.S. Gas segment also enters into contracts under which we are responsible for marketing the majority of the gas and natural gas liquids produced by the counterparties to the agreements. The majority of U.S. Gas' revenues were generated from such contracts.

Our U.S. Liquids segment has minimum volume commitments for pipeline transportation of crude oil. At December 31, 2018, the approximate amount of future obligations is as follows (in thousands):



For year ending:
December 31, 2019	$	21,865
December 31, 2020	19,751
December 31, 2021	12,976
December 31, 2022	13,231
December 31, 2023	13,496
Thereafter	6,816
Total expected future payments	$	88,135

Capital expenditures

We have commitments to spend approximately $104.4 million in 2019 related to property, plant and equipment.

Redeemable Preferred Stock (Notes)	12 Months Ended
Redeemable Preferred Stock (Notes)	Dec. 31, 2018
Redeemable Preferred Stock [Abstract]
Preferred Stock [Text Block]	REDEEMABLE PREFERRED STOCK On January 19, 2018 (the “Issue Date”), we issued and sold to WP SemGroup Holdings L.P. (“Warburg”) and certain other investors an aggregate of 350,000 shares of Series A Cumulative Perpetual Convertible Preferred Stock, par value $0.01 per share, of the Company (the “Preferred Stock”), convertible into shares of the Company’s Class A Common Stock, par value $0.01 per share (the “Common Stock”), for a cash purchase price of $1,000 per share of Preferred Stock and aggregate gross proceeds to the Company of $350,000,000, which proceeds were utilized (i) to repay amounts borrowed under the Company’s revolving credit facility, (ii) to fund growth capital expenditures and (iii) for general corporate purposes. The Preferred Stock was recorded on our condensed consolidated balance sheets net of $7.7 million of issuance costs. The Preferred Stock is a new class of equity security that ranks senior to the Common Stock with respect to distribution rights and rights upon liquidation. Subject to certain exceptions, so long as any Preferred Stock remains outstanding, no dividend or distribution will be declared or paid on, and no redemption or repurchase will be agreed to or consummated of, stock on a parity with the Preferred Stock (“Parity Stock”), Common Stock or any other shares of stock junior to the Preferred Stock, unless all accumulated and unpaid dividends for all preceding full fiscal quarters have been declared and paid with respect to the Preferred Stock. In addition, no dividend or distribution or redemption or repurchase shall be paid on Parity Stock, Common Stock or any other shares of stock junior to the Preferred Stock for any period unless the Preferred Stock has been paid full cash dividends in respect of the same period; provided, however, that the Company may pay dividends on Common Stock in respect of any fiscal quarter ending on or prior to June 30, 2020 (the “PIK Period”). The holders of Preferred Stock (the “Holders”) will receive quarterly distributions equal to an annual rate of 7.0% ($70.00 per share annualized) of $1,000 per share of Preferred Stock, subject to certain adjustments (the “Liquidation Preference”). With respect to any quarter ending on or prior to the PIK Period, the Company may elect, in lieu of paying a distribution in cash, to have the amount that would have been payable if such dividend had been paid in cash added to the Liquidation Preference. On or after the eighteen month anniversary of the Issue Date, the Holders may convert their Preferred Stock into a number of shares of Common Stock equal to, per share of Preferred Stock, the quotient of the Liquidation Preference divided by $33.00 (the “Conversion Price”), subject to certain adjustments including customary anti-dilution adjustments (such quotient, the “Conversion Rate”). Holders may elect to convert the Preferred Stock, in whole or in part, so long as the aggregate value of Common Stock to be issued pursuant to such partial conversion is not for less than $50,000,000 or a lesser amount if such conversion relates to all of a Holder’s remaining Preferred Stock. On or after the three year anniversary of the Issue Date, if the Holders have not elected to convert all of their shares of Preferred Stock, the Company may cause the outstanding Preferred Stock to be converted into a number of shares of Common Stock equal to, per share of Preferred Stock, the quotient of the Liquidation Preference divided by the Conversion Price, subject to certain adjustments including customary anti-dilution adjustments; provided, that in order for the Company to exercise such conversion right, the closing sale price of the Common Stock during a designated period be greater than or equal to $47.85, the resale of the shares of Common Stock issuable upon conversion shall be registered and available for resale by the Holders pursuant to a registration statement declared effective by the SEC covering such resales, the Common Stock is listed on a national securities exchange, and certain average daily trading volume minimum requirements are met. The Company may elect to convert the Preferred Stock, in whole or in part, so long as the aggregate value of Common Stock to be issued pursuant to such partial conversion is not for less than $50,000,000 or such lesser amount if such conversion relates to the aggregate amount of all remaining Preferred Stock. Upon a change of control that involves consideration that is at least 90% cash, Holders are required to convert their shares of Preferred Stock into Common Stock at a rate equal to the greater of (i) the product of the Conversion Rate and the quotient of (a) the product of the Conversion Price and the Cash Change of Control Conversion Premium (as defined below), divided by (b) the average volume weighted average price of the Common Stock during a designated period and (ii) the Conversion Rate otherwise in effect at such time. The “Cash Change of Control Conversion Premium” equals (i) on or prior to the first anniversary of the Issue Date, 130%, (ii) after the first anniversary of the Issue Date, but on or prior to the second anniversary of the Issue Date, 120%, (iii) after the second anniversary of the Issue Date, but on or prior to the third anniversary of the Issue Date, 105%, and (iv) thereafter, 101%. Upon a change of control that involves consideration that is less than 90% cash, Holders may elect to: (i) convert all, but not less than all, outstanding shares of Preferred Stock into Common Stock at the then-applicable Conversion Rate; (ii) except as described below, if the Company will not be the surviving person upon the consummation of such change of control, require the Company to use its commercially reasonable efforts to deliver to the Holders a security in the surviving person or the parent of the surviving person that has rights, preferences and privileges substantially similar to the Preferred Stock; provided, however, that, if the Company is unable to do so, such Holders shall be entitled to: (A) instead elect to convert shares of Preferred Stock pursuant to the mechanics described in clause (i) above or (B) require the Company to redeem all (but not less than all) of such Holder’s Preferred Stock at a price per share equal to 101% of the Liquidation Preference, with the redemption price being paid (at the Company’s option): (1) in cash or (2) in Common Stock; (iii) if the Company is the surviving person upon the consummation of such change of control, continue to hold such Holders’ shares of Preferred Stock; or (iv) require the Company to redeem all (but not less than all) of such Holder’s Preferred Stock at a cash price per share equal to the Liquidation Preference. At December 31, 2018, a change in control is not considered probable. Holders shall be entitled to vote on all matters on which the holders of shares of Common Stock are entitled to vote and, except as otherwise provided in the Certificate of Incorporation, or by law, the Holders shall vote together with the holders of shares of Common Stock as a single class. Each Holder is entitled to a number of votes equal to the number of votes such Holder would have had if all shares of Preferred Stock held by such Holder had been converted into shares of Common Stock. So long as any Preferred Stock is outstanding, the affirmative vote or consent of the Holders of at least 66 2/3% of the outstanding Preferred Stock, voting together as a separate class, will be necessary for effecting or validating: (i) any issuance of stock senior to the Preferred Stock, (ii) any issuance by the Company of Parity Stock, subject to certain exceptions described below, (iii) any repurchase by the Company of any Preferred Stock, other than on a pro rata basis among all Holders of Preferred Stock, (iv) any special, one-time dividend or distribution with respect to any class of junior stock and (v) any spinoff or other distribution of any equity securities or assets of any of the Company’s subsidiaries to its stockholders in which the consideration received by the Company in such transaction is less than fair market value, subject to certain exceptions. However, the foregoing rights of the Holders will not restrict any of the following actions, subject to certain terms: (i) the Company and any of its controlled affiliates entering into joint ventures with third parties, (ii) the issuance of securities, capital contributions or incurrence of intercompany indebtedness among the Company or any of its subsidiaries, or (iii) the issuance of securities, capital contributions or incurrence of intercompany indebtedness among the Company and any joint ventures, partnerships or other minority owned entities in which the Company or its subsidiaries have an equity or other interest, in each case, which exist as of the Issue Date. Notwithstanding the vote or consent of the Holders described above, after the Issue Date, the Company may issue certain amounts of Parity Stock without the approval of the Holders if: (A) the aggregate amount of such issuances is less than or equal to $250,000,000 (excluding the aggregate amount of any additional shares of Preferred Stock issued to Warburg); or (B) the aggregate initial purchase price of the then outstanding Preferred Stock is less than $100,000,000. Prior to the first anniversary of the Issue Date, no Holder may transfer any Preferred Stock without the prior written consent of the Company. Prior to the second anniversary of the Issue Date, Holders and their affiliates are prohibited from directly or indirectly engaging in any short sales or other hedging transactions involving the Preferred Stock and Common Stock underlying such Holder’s Preferred Stock. For so long as Warburg and its affiliates collectively own 75% or more of the outstanding Preferred Stock acquired by Warburg and its affiliates on the Issue Date, the Company, prior to any issuance of Parity Stock, is required to provide Warburg with a reasonable opportunity to purchase all or any portion of such shares of Parity Stock to be issued by the Company on substantially the same terms offered to the other purchasers of such securities. The terms of the Preferred Stock purchase agreement (the “Purchase Agreement”) contains customary representations, warranties and covenants of the Company and the Purchasers made as of the date of the Purchase Agreement and as of the Issue Date, and the parties have agreed to indemnify each other against certain losses resulting from breaches of their respective representations, warranties and covenants. Pursuant to the Purchase Agreement, the Company has granted to Warburg, until Warburg no longer owns at least 50% of the Preferred Stock issued to Warburg and its affiliates on the Issue Date, certain rights to designate an observer (the “Board Observer”) to the board of directors of the Company (the “Board”), who shall have the right to attend full meetings of the Board (including any executive session and certain committees thereof) and receive such materials as other members of the Board receive. In addition, pursuant to the Purchase Agreement, the Company also granted Warburg and its affiliates rights to require the Company to file and maintain, subject to the penalties described in the Purchase Agreement, registration statements with respect to the resale of the Common Stock issuable upon conversion of the Preferred Stock. The Company is required to file or cause to be filed a registration statement (the “Preferred Registration Statement”) for the resale of registrable securities and is required to cause the Preferred Registration Statement to become effective no later than the eighteen month anniversary of the Issue Date. In certain circumstances, Warburg and its affiliates will have piggyback registration rights on offerings initiated by the Company or other persons who have been granted registration rights, and Warburg has the right to request two underwritten offerings upon certain terms and conditions set forth in the Purchase Agreement. Holders of registrable securities will cease to have registration rights under the Purchase Agreement on the earlier of (i) the second anniversary of the date on which shares Preferred Stock are first converted into shares of Common Stock and (ii) the date on which no registrable securities remain outstanding; provided, that the Company shall use reasonable best efforts to maintain the effectiveness of the Preferred Registration Statement during all periods in which Warburg (A) is deemed to be an affiliate of the Company pursuant to Rule 144 under the Securities Act of 1933, as amended (the “Securities Act”), or (B) together with its affiliates, owns more than 5% of the Company’s Common Stock (including Common Stock it would own on an as-converted basis). On May 25, 2018, we paid-in-kind a preferred stock dividend of $4.8 million, which was prorated for the period from January 19, 2018 to March 31, 2018. On August 29, 2018, we paid-in-kind a preferred stock dividend of $6.2 million. On November 26, 2018, we paid-in-kind a preferred stock dividend of $6.3 million. These dividends paid-in-kind increased the Liquidation Preference such that as of December 31, 2018, the Preferred Stock was convertible into 11,132,121 shares. On February 20, 2019, we declared a preferred stock dividend to be paid-in-kind of $6.4 million, which will be paid on March 01, 2019.

Equity

12 Months Ended

Dec. 31, 2018

Stockholders' Equity Note [Abstract]

Equity

EQUITY

Common stock

The common stock for which the par value is reflected on the consolidated balance sheet at December 31, 2018 is summarized below:



	Class A
Shares accounted for at December 31, 2015	43,823,739
Issuance of common shares in public offering	8,625,000
Shares issued for Merger	13,140,020
Issuance of shares under employee and director compensation programs⁽¹⁾	170,772
Shares issued under employee stock purchase plan	46,836
Shares accounted for at December 31, 2016	65,806,367
Shares issued for HFOTCO acquisition	12,383,900
Issuance of shares under employee and director compensation programs⁽¹⁾	149,961
Shares issued under employee stock purchase plan	39,545
Shares accounted for at December 31, 2017	78,379,773
Issuance of shares under employee and director compensation programs⁽¹⁾	202,545
Shares issued under employee stock purchase plan	53,757
Shares accounted for at December 31, 2018⁽²⁾	78,636,075

(1) Of these vested shares, recipients sold back to the Company 57,041, 42,347 and 46,941 shares during the years ended December 31, 2018, 2017 and 2016, respectively, to satisfy tax withholding obligations. These repurchased shares are being recognized at cost as treasury stock on the consolidated balance sheet.

(2) In addition to the shares in the table above, there are shares of unvested restricted stock outstanding which are considered legally issued and outstanding and have been included in the number of shares presented on the consolidated balance sheets. The par value of unvested restricted stock has not yet been reflected in common stock on the consolidated balance sheet, as these shares have not yet vested and could be forfeited. There are also shares of restricted stock that were returned to treasury upon forfeiture. The par value of these shares is not reflected in the consolidated balance sheet, as no accounting recognition is given to forfeited shares.

The common stock includes Class A and Class B stock. Class A stock is eligible to be listed on an exchange, whereas Class B stock is not. Any share of Class B stock may be converted to Class A at the election of the holder. Both classes of stock have full voting rights. Both classes of stock have a par value of $0.01 per share. No Class B stock is currently issued. The total number of shares authorized for issuance is 180,000,000 shares of Class A stock and 10,000,000 shares of Class B stock.

Preferred Stock Issuances

On May 17, 2017, our stockholders voted to approve an amendment to the Company's Amended and Restated Certificate of Incorporation to authorize 4,000,000 shares of preferred stock. On January 19, 2018, we issued an aggregate of 350,000 shares of preferred stock. See Note 15 for further information on the issuance.

Equity issuances

On June 22, 2016, we issued and sold 8,625,000 shares of our Class A common stock, valued at $27.00 per share, to the public for proceeds of $228.5 million, net of underwriting fees and other offering costs of $4.3 million. Proceeds were used to repay borrowings on our revolving credit facility and for capital expenditures and general corporate purposes.

On September 30, 2016, we completed the Merger with Rose Rock. We issued 13.1 million common shares in exchange for the outstanding common limited partner units of Rose Rock which we did not already own. Issuance costs of $5.3 million were recorded as a reduction to additional paid in capital. In addition, we recorded a reduction to our deferred tax liabilities and offsetting increase to additional paid-in capital of $143.3 million associated with the transaction. This non-cash adjustment represents the deferred tax impact of the difference between the book value of the noncontrolling interests acquired and the tax basis which is stepped-up to the fair market value of the consideration which includes the common shares issued and the assumption of liabilities associated with the noncontrolling interests. See Note 5 for further information on the Merger.

On July 17, 2017, we completed the acquisition of HFOTCO. We issued 12.4 million common shares with an acquisition date fair value of $330 million, based on $26.68 per common share market price at issuance. See Note 5 for further information on the acquisition.

Noncontrolling Interest

On October 22, 2018, Maurepas Pipeline, LLC, a subsidiary of SemGroup, sold Class B shares representing a 49% ownership interest to Alinda Capital Partners (“Alinda”) for $350 million, subject to customary post-closing adjustments. The Class B shares provide Alinda with a $2.2 million monthly preference on distributions. The Class B shares are convertible to Class A shares of Maurepas Pipeline, LLC at Alinda’s option any time after the second anniversary of closing. SemGroup has a call option to repurchase Alinda’s shares prior to the fifth anniversary of closing for a fixed amount of $350 million plus 1% per annum, subject to a 24 month non-call period. The Class B shares provide Alinda with two out of five seats on the Board of Managers of Maurepas Pipeline, LLC and certain protective rights. The Class B shares are reported as a noncontrolling interest in our consolidated financial statements.

Dividends

The following table sets forth the quarterly dividends per share declared and paid to shareholders for the periods indicated:



Quarter Ending	Dividend Per Share		Date of Record	Date Paid
March 31, 2016	$	0.45	March 7, 2016	March 17, 2016
June 30, 2016	$	0.45	May 16, 2016	May 26, 2016
September 30, 2016	$	0.45	August 15, 2016	August 25, 2016
December 31, 2016	$	0.45	November 18, 2016	November 28, 2016

March 31, 2017	$	0.45	March 7, 2017	March 17, 2017
June 30, 2017	$	0.45	May 15, 2017	May 26, 2017
September 30, 2017	$	0.45	August 18, 2017	August 28, 2017
December 31, 2107	$	0.45	November 20, 2017	December 1, 2017

March 31, 2018	$	0.4725	March 9, 2018	March 19, 2018
June 30, 2018	$	0.4725	May 16, 2018	May 25, 2018
September 30, 2018	$	0.4725	August 20, 2018	August 29, 2018
December 31, 2018	$	0.4725	November 16, 2018	November 26, 2018

March 31, 2019	$	0.4725	March 4, 2019	March 14, 2019

Rose Rock Midstream, L.P.

The following table shows the distributions paid by Rose Rock Midstream, L.P., prior to the Merger, related to the earnings for each of the following periods (in thousands, except for per unit amounts):



	Distribution Per Unit		Distributions Paid
Quarter Ended			SemGroup								Noncontrolling Interest Common Units		Total Distributions
Quarter Ended			General Partner		Incentive Distributions		Common Units		Subordinated Units		Noncontrolling Interest Common Units		Total Distributions
December 31, 2015	$	0.6600	$	604	$	5,333	$	13,665	$	—	$	10,622	$	30,224

March 31, 2016	$	0.6600	$	605	$	5,338	$	13,665	$	—	$	10,643	$	30,251
June 30, 2016	$	0.6600	$	605	$	5,339	$	13,665	$	—	$	10,648	$	30,257

Accumulated Other Comprehensive Income (Loss)

12 Months Ended

Dec. 31, 2018

Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]

Accumulated Other Comprehensive Income (Loss)

ACCUMULATED OTHER COMPREHENSIVE LOSS

The following table presents changes in the components of accumulated other comprehensive loss (in thousands):



	Currency Translation			Employee Benefit Plans			Total
Balance, December 31, 2015	$	(57,201	)	$	(1,361	)	$	(58,562	)
Currency translation adjustment, net of income tax benefit of $8,672	(14,224		)	—			(14,224		)
Changes related to benefit plans, net of income tax benefit of $417	—			(1,128		)	(1,128		)
Balance, December 31, 2016	(71,425		)	(2,489		)	(73,914		)
Currency translation adjustment, net of income tax expense of $12,404	20,411			—			20,411
Changes related to benefit plans, net of income tax expense of $99	—			(298		)	(298		)
Balance, December 31, 2017	(51,014		)	(2,787		)	(53,801		)
Currency translation adjustment, net of income tax benefit of $4,949	(32,379		)	—			(32,379		)
Currency translation adjustment reclassified to gain on disposal, net of income tax expense of $11,769	37,577			—			37,577
Changes related to benefit plans, net of income tax benefit of $311	—			(2,644		)	(2,644		)
Balance, December 31, 2018	$	(45,816	)	$	(5,431	)	$	(51,247	)

There were no significant items reclassified out of accumulated other comprehensive loss to net income for the years ended December 31, 2017 and 2016.

Revenue Revenue

12 Months Ended

Dec. 31, 2018

Revenue from Contract with Customer [Abstract]

Revenue from Contract with Customer [Text Block]

18.

REVENUE FROM CONTRACTS WITH CUSTOMERS

We provide gathering, transportation, storage, distribution, marketing and other midstream services primarily to producers, refiners of petroleum products and other market participants located in the Gulf Coast, Midwest and Rocky Mountain regions of the United States of America (the “U.S.”) and Western Canada. In general, we recognize service revenue as the service is performed (“over time”) and product sales revenues are recognized when control of the product transfers to the customer (“point in time”). Our revenue from contracts with customers are disaggregated by segment as follows:

U.S. Liquids


•	U.S. Liquids generates revenue by:


◦	providing crude oil pipeline and truck transportation services to customers under fee-based contractual arrangements generally based on units of volume transported;


◦	providing crude oil storage services primarily to customers in the Houston Ship Channel and at the Cushing Hub under fee-based contractual arrangements that, in some cases, are fixed and not dependent on usage;


◦	providing terminalling services including pump-over, unloading, heating, berthing and excess throughput fees which are based on per volume fees for units delivered or withdrawn; and

◦

performing marketing activities including purchasing crude oil for its own account from producers and aggregators and selling to traders and refiners under contracts generally with initial terms of less than one year. Revenue is recognized based on market prices at the time the commodities are sold. In certain transactions, we purchase inventory from, and sell inventory to, the same counterparty. Such transactions that are entered into in contemplation of one another are recorded on a net basis.

U.S. Liquids also generates revenue from leases of certain land, tanks and a barge dock, which are accounted for as a direct financing lease and are outside of the scope of ASC 606.

U.S. Gas

•

U.S. Gas generates revenue by providing natural gas and natural gas liquids gathering and processing services to customers based on agreements that are a combination of percent of proceeds and fee-based contracts. Initial contract terms can range from monthly and interruptible to the life of the reserves and, upon expiration, continue to renew on a month-to-month or year-to-year evergreen basis. U.S. Gas’ customers include producers, operators, marketers and traders. Gathering and processing fees are generally based on per volume fees. Product sales revenue is generated from the sale of NGLs and residue gas arising from processing at prevailing market prices.

Canada

•

Canada generates revenue from its processing plants through volumetric fees for services under contractual arrangements with working interest owners and third-party customers and the pass through of certain operating costs. Pass-through cost recoveries are reported as "Other revenue" in the consolidated statements of operations and comprehensive income (loss). Canada also derives revenue as the owner and operator of pipeline gathering systems that gather gas from multiple wells located in the same production unit and as the owner and operator of pipeline transportation systems that deliver the gathered gas to its processing plant. Canada’s customers include producers of varying sizes. To support operations at our plants, several producers have committed to process all of their current and future natural gas production.

Corporate and Other


•	Corporate and Other is not an operating segment, but contains the results of operations for our former U.K. and Mexican businesses which were disposed of in early 2018.

Key areas of judgment

Take or pay

Contracts with take-or-pay provisions are recognized over time as the customer simultaneously receives and consumes the benefit of available capacity. Payments made for unused take-or-pay capacity, which allow the customer to carryforward a portion of the unused capacity to future periods, are deferred until it becomes unlikely that the capacity will be used prior to contract expiration. Determining when, or if, the capacity will be used requires judgment.

Percentage of proceeds

Contracts with percentage of proceeds terms typically involve the receipt of natural gas at the wellhead and include gathering, processing and marketing of the resulting NGLs and residue gas with SemGroup retaining a portion of the proceeds from the ultimate sale to a third-party. The terms of these agreements include various gathering and processing fees. The determination of whether the transaction is a purchase at the wellhead by SemGroup with gathering and processing performed on our own account or whether the transaction represents gathering and processing as a service provided to the producer by SemGroup with a purchase and sale of processed gas at the completion of the service, requires judgment and is impacted by when control of the underlying commodity has been deemed to move from the producer to the processor. This determination impacts whether gathering and processing fees are recorded as reductions to cost of sales or recorded as service revenue.

Principal vs. agent

We engage in various types of transactions where we perform marketing activities for producers, such as our percentage of proceeds contracts, or transactions where costs are incurred and reimbursed by customers or other owners in facilities, such as Canada's pass-through costs. These types of transactions require judgment to determine whether we are the principal or an agent in the transaction and as a result whether revenues are recorded gross or net.

Non-cash consideration

SemGroup receives commodities from its customers in the form of plant and field fuel, pipeline loss allowance and retention of drip liquids. The purpose of the receipt of these commodities is to keep the Company whole in the case of

minor operational usage or loss of product and is not intended as a consideration for services performed. Therefore, the receipt of these commodities does not represent consideration and is not recorded as revenue. Any net retention of commodities in excess of actual losses is recorded in inventory and recognized as revenue when sold.

Tiered pricing and material rights

We have certain contracts that provide customers with rates that reduce incrementally as volumes increase beyond certain thresholds. These types of agreements require judgment to determine if the option for the customer to acquire additional services constitutes a material right that the customer would not receive without entering into the contract, e.g. the discount exceeds the range of discounts typically given. If it is determined that a material right exists, a portion of the revenue is allocated to that right at contract inception and recognized as revenue as the option for additional services is exercised or when the option expires. In contrast, if it is concluded that the option to acquire additional services reflects standalone selling price, this would constitute a marketing offer and not a material right.

Disaggregated revenue

Our revenue is disaggregated by segment and by activity below (in thousands):



	Year Ended December 31,
	2018			2017			2016
U.S. Liquids
Product sales	$	1,680,327		$	1,299,343		$	716,570
Pipeline transportation	84,878			43,642			23,099
Truck transportation	23,553			31,351			41,754
Storage fees	161,498			85,712			27,673
Facility service fees	49,896			27,658			18,283
Lease revenue	17,549			5,843			—

U.S. Gas
Product sales	210,827			180,581			167,319
Service fees	54,494			52,637			51,651

Canada
Service fees	134,059			120,575			75,715
Other revenue	59,075			62,657			57,501

Corporate and Other
Product sales	31,319			153,164			136,448
Storage fees	7,753			22,764			20,542
Service fees	3,070			7,160			6,537
Intersegment eliminations	(15,036		)	(11,170		)	(10,928		)

Total revenue	$	2,503,262		$	2,081,917		$	1,332,164

Remaining performance obligations

Most of our service contracts are such that we have the right to consideration from a customer in an amount that corresponds directly with the value to the customer of our performance completed to date. Therefore, we are utilizing the practical expedient in ASC 606-10-55-18 under which we recognize revenue in the amount to which we have the right to invoice. Applying this practical expedient, we are not required to disclose the transaction price allocated to remaining performance obligations under these agreements. However, certain of our agreements, such as "take-or-pay" agreements, do not qualify for the practical expedient. The amount and timing of revenue recognition for such contracts is presented below (in thousands):



	2019		2020		2021		2022		2023		Thereafter
Expected timing of revenue recognized for remaining performance obligations	$	280,984	$	227,981	$	186,465	$	169,252	$	163,193	$	1,349,773

For our product sales contracts, we have elected the practical expedient set out in ASC 606-10-50-14A that states that we are not required to disclose the transaction price allocated to remaining performance obligations if the variable consideration is allocated entirely to a wholly unsatisfied performance obligation. Under these agreements, each unit of product represents a separate performance obligation and therefore future volumes are wholly unsatisfied and disclosure of transaction price allocated to remaining performance obligations is not required. Under product sales contracts, the variability arises as both volume and pricing (typically index based) are not known until the product is delivered.

Receivables from contracts with customers

Accounts receivable, net on the condensed consolidated balance sheets represents current receivables from contracts with customers. Certain noncurrent receivables from contracts with customers are included in “other noncurrent assets” on the condensed consolidated balance sheets. These amounts are accruals to recognize revenue for performance to date related to customer deficiencies on minimum volume commitments with make-up rights for which the use of the make-up rights are not probable due to capacity constraints or other factors. Therefore, we have accrued the amount for which no future performance by SemGroup will be required, but for which we do not have a present right to bill the customer until the end of the contract. The balance of noncurrent receivables from customer contracts was (in thousands):



	December 31, 2018		December 31, 2017
Noncurrent receivables	$	11,496	$	—

Noncurrent receivables for the transactions described above were not recorded prior to the adoption of ASC 606 as our policy was to defer recognition of deficiencies with make-up rights until the contractual make-up rights expired.

Deferred revenue

We record deferred revenue when we have received a payment in advance of delivering a product or performing a service. For the year ended December 31, 2018, we recognized $4.2 million of revenue which was included in deferred revenue at the beginning of the period.

Costs to obtain or fulfill a contract

Unless material, we expense costs to obtain or fulfill a contract in the period incurred. At December 31, 2018, we had contract assets of $9.4 million related to costs incurred to obtain contracts which had been expensed as incurred under previous guidance. These costs are reported within “other noncurrent assets” on the condensed consolidated balance sheets and are being amortized straight-line over 25 years, the life of the related contracts. We recognized $0.4 million of amortization of these assets for the year ended December 31, 2018.

Earnings Per Share

12 Months Ended

Dec. 31, 2018

Earnings Per Share [Abstract]

Earnings Per Share

EARNINGS PER SHARE

Earnings per share is calculated based on income from continuing and discontinued operations less any income attributable to noncontrolling interests and cumulative preferred stock dividends. Prior to completion of the Merger in 2016, income attributable to noncontrolling interests represented third-party limited partner unitholders' interests in the earnings of our consolidated subsidiary, Rose Rock. Rose Rock allocated net income to its limited partners based on the distributions pertaining to the current period's available cash as defined by Rose Rock's partnership agreement. After adjusting for the appropriate period's distributions, the remaining undistributed earnings or excess distributions over earnings, if any, were allocated to Rose Rock's general partner, limited partners and participating securities in accordance with the contractual terms of Rose Rock's partnership agreement and as further prescribed under the two-class method. Incentive distribution rights did not participate in undistributed earnings. Subsequent to the Merger, there is no longer a noncontrolling interest for Rose Rock. In 2018, Maurepas Pipeline, LLC, a subsidiary of SemGroup, sold Class B shares representing a 49% interest in the form of Class B shares of Maurepas Pipeline, LLC. The Class B shares provide for a monthly preference on Maurepas Pipeline, LLC distributions and are reported as a noncontrolling interest.

Basic earnings (loss) per share is calculated based on the weighted average shares outstanding during the period. Diluted earnings (loss) per share includes the dilutive effect of unvested equity compensation awards and the potential conversion of preferred stock, if dilutive.

The following summarizes the calculation of basic earnings per share for the years ended December 31, 2018, 2017 and 2016 (in thousands, except per share amounts):



	Year Ended December 31, 2018
	Continuing Operations			Discontinued Operations		Net
Loss	$	(24,328	)	$	—	$	(24,328	)
less: Income attributable to noncontrolling interest	2,421			—		2,421
Loss attributable to SemGroup	$	(26,749	)	$	—	$	(26,749	)
less: cumulative preferred stock dividends	23,790			—		23,790
Net loss attributable to common shareholders	(50,539		)	—		(50,539		)
Weighted average common stock outstanding	78,313			78,313		78,313
Basic loss per share	$	(0.65	)	$	—	$	(0.65	)



	Year Ended December 31, 2017
	Continuing Operations			Discontinued Operations		Net
Loss	$	(17,150	)	$	—	$	(17,150	)
less: Income attributable to noncontrolling interest	—			—		—
Loss attributable to SemGroup	$	(17,150	)	$	—	$	(17,150	)
Weighted average common stock outstanding	71,418			71,418		71,418
Basic loss per share	$	(0.24	)	$	—	$	(0.24	)



	Year Ended December 31, 2016
	Continuing Operations		Discontinued Operations			Net
Income	$	13,263	$	(1	)	$	13,262
less: Income attributable to noncontrolling interest	11,167		—			11,167
Income attributable to SemGroup	$	2,096	$	(1	)	$	2,095
Weighted average common stock outstanding	51,889		51,889			51,889
Basic earnings per share	$	0.04	$	—		$	0.04

The following summarizes the calculation of diluted earnings per share for the years ended December 31, 2018, 2017 and 2016 (in thousands, except per share amounts):



	Year Ended December 31, 2018
	Continuing Operations			Discontinued Operations		Net
Loss	$	(24,328	)	$	—	$	(24,328	)
less: Income attributable to noncontrolling interest	2,421			—		2,421
Loss attributable to SemGroup	$	(26,749	)	$	—	$	(26,749	)
Less: cumulative preferred stock dividends	23,790			—		23,790
Net loss attributable to common shareholders	(50,539		)	—		(50,539		)
Weighted average common stock outstanding	78,313			78,313		78,313
Effect of dilutive securities	—			—		—
Diluted weighted average common stock outstanding	78,313			78,313		78,313
Diluted loss per share	$	(0.65	)	$	—	$	(0.65	)



	Year Ended December 31, 2017
	Continuing Operations			Discontinued Operations		Net
Loss	$	(17,150	)	$	—	$	(17,150	)
less: Income attributable to noncontrolling interest	—			—		—
Loss attributable to SemGroup	$	(17,150	)	$	—	$	(17,150	)
Weighted average common stock outstanding	71,418			71,418		71,418
Effect of dilutive securities	—			—		—
Diluted weighted average common stock outstanding	71,418			71,418		71,418
Diluted loss per share	$	(0.24	)	$	—	$	(0.24	)



	Year Ended December 31, 2016
	Continuing Operations		Discontinued Operations			Net
Income	$	13,263	$	(1	)	$	13,262
less: Income attributable to noncontrolling interest	11,167		—			11,167
Income attributable to SemGroup	$	2,096	$	(1	)	$	2,095
Weighted average common stock outstanding	51,889		51,889			51,889
Effect of dilutive securities	392		392			392
Diluted weighted average common stock outstanding	52,281		52,281			52,281
Diluted earnings per share	$	0.04	$	—		$	0.04

For the year ended December 31, 2018, the preferred stock would have been antidilutive and therefore, was not included in the computation of diluted earnings. For the years ended December 31, 2018 and 2017, we experienced net losses attributable to SemGroup. The unvested equity compensation awards would have been antidilutive and, therefore, were not included in the computation of diluted earnings per share.

Equity-Based Compensation

12 Months Ended

Dec. 31, 2018

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Equity-Based Compensation

EQUITY-BASED COMPENSATION

SemGroup Corporation equity awards

We have reserved a total of 3,710,220 shares of common stock for issuance pursuant to employee and director compensation programs. Awards under these programs give the recipients the right to receive shares of common stock, once specified service, performance or market related vesting conditions are met. The awards typically have a one year

vesting period for non-management directors and three years for employees. The awards may be subject to accelerated vesting in the event of involuntary terminations. We record expense for these awards (and corresponding increases to additional paid-in capital) based on the grant date fair value of the awards over the vesting period. We use authorized but unissued shares to satisfy our equity-based payment obligations. Although these awards are to be settled in shares, we may elect to give participants the option of surrendering a portion of the awards, to meet statutory minimum tax withholding requirements. The activity related to these awards during the period from December 31, 2015 to December 31, 2018 is summarized below:



	Unvested Shares		Average Grant Date Fair Value		Aggregate Fair Value of Shares (in thousands)
Outstanding at December 31, 2015	411,308		$	75.25
Awards granted - 2016	702,309		$	19.18
Awards vested - 2016	(168,096	)	$	20.38	$	3,426
Awards forfeited - 2016	(34,255	)	$	42.42
Outstanding at December 31, 2016	911,266		$	31.09
Awards granted - 2017	377,766		$	35.22
Awards vested - 2017	(149,961	)	$	33.60	$	5,039
Awards forfeited - 2017	(54,981	)	$	81.80
Outstanding at December 31, 2017	1,084,090		$	29.07
Awards granted - 2018	781,100		$	22.10
Awards vested - 2018	(202,545	)	$	23.18	$	4,695
Awards forfeited - 2018	(188,410	)	$	49.72
Outstanding at December 31, 2018	1,474,235		$	21.04

Of the awards vested during the years ended December 31, 2018, 2017 and 2016, 57,041, 42,347 and 46,941 shares were withheld to satisfy minimum tax requirements, respectively.

Included in the awards granted for the year ended December 31, 2016, is 128,585 restricted stock awards granted in exchange for Rose Rock equity based awards which were canceled as part of the Merger transaction described in Note 5. Incremental compensation expense was not significant. Accrued unvested unit distribution rights associated with unvested Rose Rock restricted unit awards carried over to the restricted stock awards issued in the exchange.

For certain of the awards granted in 2018, 2017, and 2016, the number of shares that will vest is contingent upon our achievement of certain specified targets. Awards with performance conditions are valued based on the grant date closing price on the New York Stock Exchange based on the number of awards expected to vest. Awards with market conditions are valued using Monte Carlo simulations and were granted in 2017 and 2016. There were no awards with market conditions granted in 2018. The following table sets forth the assumptions used in the valuations of these awards granted in 2017 and 2016:



	2017	2016
Volatility	54.2%	51.9%
Risk-free interest rate	1.57%	0.98%

Volatility assumptions were based on historical volatility using a simple average calculation of volatility over a period equal to the vesting period of the awards. We do not expect future volatility over the term of the awards to be significantly different from historical volatility.

If we meet the specified maximum targets, approximately 558 thousand additional shares could vest.

The holders of certain restricted stock awards are entitled to equivalent dividends (“UDs”) to be settled in cash upon vesting of the restricted stock awards. The UDs are subject to the same forfeiture and acceleration conditions as the associated restricted stock awards. At December 31, 2018, the value of UDs related to unvested restricted stock awards was approximately $2.7 million.

Compensation costs expensed for restricted stock awards for the years ended December 31, 2018, 2017 and 2016 were $11.4 million, $10.1 million and $8.8 million, respectively. As of December 31, 2018, there was $13.9 million of total unrecognized compensation cost related to our non-vested restricted stock awards, which is expected to be recognized over a weighted-average period of 16 months.

Director retainer

For the year ended December 31, 2016, we issued 2,676 shares of common stock to a director, in lieu of an annual cash retainer. No shares were issued to directors in lieu of an annual cash retainer for the years ended December 31, 2017 and 2018.

Employee stock purchase plan

Our employee stock purchase plan ("ESPP") allows eligible employees to contribute up to 10% of their base earnings toward the semi-annual purchase of our common stock, subject to an annual maximum dollar amount. The purchase price is 85% of the closing price on the last business day of the offering period. We have reserved a total of 1,000,000 shares of common stock for issuance under the ESPP. During the years ended December 31, 2018, 2017 and 2016, we issued 53,757, 39,545 and 46,836 shares, respectively, under our ESPP.

Rose Rock equity-based compensation

Prior to the Merger, certain of our employees who supported Rose Rock participated in Rose Rock's equity-based compensation program. Awards under this program generally represented awards of restricted common units representing limited partner interests of Rose Rock. Generally, the awards vested three years after the date of grant for employees and one year after the date of grant for non-management directors, contingent upon the continued service of the recipients and may have been subject to accelerated vesting in the event of involuntary terminations. Awards were valued based on the grant date closing price listed on the New York Stock Exchange. Compensation expense was recognized over the vesting period and was discounted for estimated forfeitures. Vesting of these awards diluted our ownership interest. The activity related to these awards is summarized below:



	Unvested Units		Average Grant Date Fair Value		Aggregate Fair Value of Units (in thousands)
Outstanding at December 31, 2015	100,191		$	38.70
Awards granted - 2016	117,204		$	9.62
Awards vested - 2016	(57,458	)	$	11.58	$	665
Awards forfeited - 2016	(1,846	)	$	26.55
Awards converted to SemGroup awards	(158,091	)	$	19.57
Outstanding at December 31, 2016	—		$	—

Of the awards vested during the year ended December 31, 2016, 254 were withheld to satisfy minimum tax requirements.

Compensation cost expensed for the year ended December 31, 2016, was $1.2 million and represents an increase in noncontrolling interests in consolidated subsidiaries.

The holders of certain of these restricted unit awards were entitled to equivalent distributions (“UUDs”) to be received upon vesting of the restricted unit awards. As part of the Merger transaction, the value of these cash settled UUDs related to unvested restricted units was transferred to SemGroup and is now included in the balance for SemGroup UD's noted above.

Segments

12 Months Ended

Dec. 31, 2018

Segment Reporting [Abstract]

Segments

21.

SEGMENTS

As described in Note 1, our businesses are organized based on the nature and location of the services they provide. Certain summarized information related to our reportable segments is shown in the tables below. None of the operating segments have been aggregated. Although Corporate and Other does not represent an operating segment, it is included in the tables below to reconcile segment information to that of the consolidated Company.

In the fourth quarter of 2018, due to recent changes in our asset portfolio, the company elected to reorganize its business structure and reporting relationships to enhance execution and capture operating efficiencies. In conjunction with the reorganization, our reportable segments have changed. Prior period segment disclosures have been recast to reflect the new segments. U.S. Liquids includes the results of our U.S. crude oil operations, including the results of HFOTCO, subsequent to its acquisition in 2017. U.S. Gas contains the results of our historical SemGas segment. Canada includes the operations of our historical SemCAMS segment. Our prior SemMexico and SemLogistics segments are included within Corporate and Other, as these businesses were disposed of in 2018. Eliminations of transactions between segments are also included within Corporate and Other in the tables below.

The accounting policies of each segment are the same as the accounting policies of the consolidated Company. Transactions between segments are generally recorded based on prices negotiated between the segments.

Segment Profit is defined as revenue, less cost of products sold (exclusive of depreciation and amortization) and operating expenses, plus equity earnings and is adjusted to remove unrealized gains and losses on commodity derivatives and to reflect equity earnings on an EBITDA basis. Reflecting equity earnings on an EBITDA basis is achieved by adjusting equity earnings to exclude our percentage of interest, taxes, depreciation and amortization from equity earnings for operated equity method investees. For our investment in NGL Energy, we exclude equity earnings and include cash distributions received.

Our results by segment are presented in the tables below (in thousands):



	Year Ended December 31,
	2018			2017			2016
Revenues:
U.S. Liquids
External	$	2,017,701		$	1,493,548		$	827,379
U.S. Gas
External	250,285			222,048			208,042
Intersegment	15,036			11,170			10,928
Canada
External	193,134			183,232			133,216
Corporate and Other
External	42,142			183,089			163,527
Intersegment	(15,036		)	(11,170		)	(10,928		)
Total Revenues	$	2,503,262		$	2,081,917		$	1,332,164

	Year Ended December 31,
	2018			2017			2016
Earnings from equity method investments:
U.S. Liquids	$	57,625		$	67,345		$	71,569
Corporate and Other	47			(14		)	2,147
Total earnings from equity method investments	$	57,672		$	67,331		$	73,716

	Year Ended December 31,
	2018			2017			2016
Depreciation and amortization:
U.S. Liquids	$	142,237		$	88,738		$	32,449
U.S. Gas	42,997			37,059			36,170
Canada	21,051			18,530			16,867
Corporate and Other	2,969			14,094			13,318
Total depreciation and amortization	$	209,254		$	158,421		$	98,804



	Year Ended December 31,
	2018			2017			2016
Income tax expense (benefit):
U.S. Liquids	$	575		$	362		$	—
Canada	11,018			8,863			3,667
Corporate and Other	11,711			(11,613		)	7,601
Total income tax expense (benefit)	$	23,304		$	(2,388	)	$	11,268

	Year Ended December 31,
	2018			2017			2016
Segment profit:
U.S. Liquids	$	309,423		$	229,208		$	190,768
U.S. Gas	67,070			67,805			66,530
Canada	81,330			76,274			53,264
Corporate and Other	9,726			33,236			39,534
Total segment profit	$	467,549		$	406,523		$	350,096

	Year Ended December 31,
	2018			2017			2016
Reconciliation of segment profit to net income (loss):
Total segment profit	$	467,549		$	406,523		$	350,096
Less:
Adjustment to reflect equity earnings on an EBITDA basis	19,532			26,890			28,757
Net unrealized loss (gain) related to derivative instruments	(5,053		)	40			989
General and administrative expense	91,568			113,779			84,183
Depreciation and amortization	209,254			158,421			98,804
Loss (gain) on disposal or impairment, net	(3,563		)	13,333			16,048
Interest expense	149,714			103,009			62,650
Loss on early extinguishment of debt	—			19,930			—
Foreign currency transaction loss (gain)	9,501			(4,709		)	4,759
Loss (gain) on sale or impairment of non-operated equity method investment	—			—			30,644
Other expense (income), net	(2,380		)	(4,632		)	(1,269		)
Income tax expense (benefit)	23,304			(2,388		)	11,268
Loss from discontinued operations	—			—			1
Net income (loss)	$	(24,328	)	$	(17,150	)	$	13,262

	Year Ended December 31,
	2018			2017			2016
Additions to long-lived assets, including acquisitions and contributions to equity method investments:
U.S. Liquids	$	119,064		$	2,289,218		$	240,242
U.S. Gas	31,102			100,537			21,913
Canada	218,566			113,263			34,506
Corporate and Other	1,804			18,062			28,020
Total additions to long-lived assets	$	370,536		$	2,521,080		$	324,681



	December 31,
	2018		2017
Total assets (excluding intersegment receivables):
U.S. Liquids	$	3,689,384	$	3,871,334
U.S. Gas	716,837		714,777
Canada	684,418		518,900
Corporate and Other	119,668		271,806
Total	$	5,210,307	$	5,376,817

	December 31,
	2018		2017
Equity investments:
U.S. Liquids	$	255,043	$	266,362
Corporate and Other	18,966		18,919
Total equity investments	$	274,009	$	285,281

Supplemental Cash Flow Information

12 Months Ended

Dec. 31, 2018

Supplemental Cash Flow Information [Abstract]

Supplemental Cash Flow Information

SUPPLEMENTAL CASH FLOW INFORMATION

Operating assets and liabilities

The following table summarizes the changes in the components of operating assets and liabilities, net of the effects of acquisitions (in thousands):



	Year Ended December 31,
	2018			2017			2016
Decrease (increase) in restricted cash	$	33		$	(1	)	$	(1	)
Decrease (increase) in accounts receivable	78,624			(237,394		)	(90,810		)
Decrease (increase) in receivable from affiliates	685			23,764			(19,541		)
Decrease (increase) in inventories	52,166			(17,862		)	(30,686		)
Decrease (increase) in other current assets	(3,406		)	2,947			634
Decrease (increase) in other assets	(1,636		)	(14,307		)	(297		)
Increase (decrease) in accounts payable and accrued liabilities	(78,829		)	209,982			94,687
Increase (decrease) in payable to affiliates	(3,198		)	(19,537		)	21,475
Increase (decrease) in other noncurrent liabilities	1,374			19,385			2,573
	$	45,813		$	(33,023	)	$	(21,966	)

Non-cash transactions

In connection with our acquisition of the noncontrolling interest in Rose Rock in 2016 (Note 5), we recorded a reduction to our deferred tax liabilities and offsetting increase to additional paid-in capital of $143.3 million associated with the transaction. This non-cash adjustment represents the deferred tax impact of the difference between the book value of the noncontrolling interest acquired and the tax basis which is stepped-up to the fair market value of the consideration which included the common shares issued and the assumption of liabilities associated with the noncontrolling interest.

Other supplemental disclosures

We paid cash for interest totaling $141.2 million, $82.0 million and $71.3 million for the years ended December 31, 2018, 2017 and 2016, respectively.

We paid cash for income taxes (net of refunds received) in the amount of $16.8 million, $7.2 million and $0.7 million during the years ended December 31, 2018, 2017 and 2016, respectively.

We accrued $51.3 million, $76.1 million and $1.4 million at December 31, 2018, 2017 and 2016, respectively, for purchases of property, plant and equipment.

We financed prepayments of insurance premiums of $8.0 million, $6.2 million and $4.7 million for the years ended December 31, 2018, 2017 and 2016, respectively.

Quarterly Financial Data

12 Months Ended

Dec. 31, 2018

Quarterly Financial Data [Abstract]

Quarterly Financial Data (Unaudited)

QUARTERLY FINANCIAL DATA (UNAUDITED)

Summarized information on our consolidated results of operations for the quarters during the year ended December 31, 2018 is shown below (in thousands, except per share amounts):



	First Quarter			Second Quarter				Third Quarter			Fourth Quarter			Total
Total revenues	$	661,609		$	595,794			$	633,996		$	611,863		$	2,503,262
Loss (gain) on disposal or impairment, net	(3,566		)	1,824				(383		)	(1,438		)	(3,563		)
Other operating costs and expenses	642,936			576,975				609,208			579,567			2,408,686
Total expenses	639,370			578,799				608,825			578,129			2,405,123
Earnings from equity method investments	12,614			14,351				14,528			16,179			57,672
Operating income	34,853			31,346				39,699			49,913			155,811
Other expenses, net	44,805			37,685				33,935			40,410			156,835
Income (loss) before income taxes	(9,952		)	(6,339		)		5,764			9,503			(1,024		)
Income tax expense (benefit)	23,083			(3,613		)		(2,697		)	6,531			23,304
Net income (loss)	(33,035		)	(2,726		)		8,461			2,972			(24,328		)
Less: net income attributable to noncontrolling interest	—			—				—			2,421			2,421
Net income (loss) attributable to SemGroup	(33,035		)	(2,726		)	—	8,461			551			(26,749		)
Less: cumulative preferred stock dividends	4,832			6,211				6,317			6,430			23,790
Net income (loss) attributable to common shareholders	$	(37,867	)	$	(8,937	)		$	2,144		$	(5,879	)	$	(50,539	)
Earnings (loss) per share—basic	$	(0.48	)	$	(0.11	)		$	0.03		$	(0.08	)	$	(0.65	)
Earnings (loss) per share—diluted	$	(0.48	)	$	(0.11	)		$	0.03		$	(0.08	)	$	(0.65	)

Summarized information on our consolidated results of operations for the quarters during the year ended December 31, 2017 is shown below (in thousands, except per share amounts):



	First Quarter				Second Quarter				Third Quarter				Fourth Quarter				Total
Total revenues	$	456,100			$	473,089			$	545,922			$	606,806			$	2,081,917
Loss (gain) on disposal or impairment, net	2,410				(234		)		41,625				(30,468		)		13,333
Other operating costs and expenses	447,392				465,874				549,442				579,147				2,041,855
Total expenses	449,802				465,640			—	591,067			—	548,679			—	2,055,188
Earnings from equity method investments	17,091				17,753				17,367				15,120				67,331
Operating income (loss)	23,389				25,202			—	(27,778		)	—	73,247			—	94,060
Other expenses, net	33,571				11,966				28,574				39,487				113,598
Income (loss) from continuing operations before income taxes	(10,182		)	—	13,236			—	(56,352		)	—	33,760			—	(19,538		)
Income tax expense (benefit)	95				3,625				(37,249		)		31,141				(2,388		)
Net income (loss)	$	(10,277	)		$	9,611			$	(19,103	)		$	2,619			$	(17,150	)
Earnings (loss) per share—basic	$	(0.16	)		$	0.15			$	(0.25	)		$	0.03			$	(0.24	)
Earnings (loss) per share—diluted	$	(0.16	)		$	0.15			$	(0.25	)		$	0.03			$	(0.24	)

The first quarter in the table above includes a $4.5 million out of period loss on disposal of rights-of-way related to immaterial prior period errors. The third and fourth quarters in the table above include the impact of our third quarter acquisition of HFOTCO (Note 5). The third quarter includes the impairment of goodwill and intangible assets related to our crude oil trucking operations of $26.6 million and $12.1 million, respectively. The fourth quarter includes the write-down of our Mexican asphalt and U.K. businesses to net realizable value (Note 4). We recorded impairments of $13.5 million and $76.7 million for the Mexican asphalt and U.K. businesses, respectively. The fourth quarter also includes a $150.3 million gain on the sale of Glass Mountain (Note 6).

Related Party Transactions

12 Months Ended

Dec. 31, 2018

Related Party Transactions

RELATED PARTY TRANSACTIONS

As described in Note 6, we own equity method investments in the general partner of NGL Energy and a 51% ownership interest in White Cliffs.

Transactions with NGL Energy and its subsidiaries primarily relate to marketing, leased storage and transportation services of crude oil, including buy/sell transactions. Transactions with White Cliffs primarily relate to leased storage, purchases and sales of crude oil, transportation fees for shipments on the White Cliffs Pipeline, and management fees.

In accordance with ASC 845-10-15, the buy/sell transactions with NGL Energy and White Cliffs were reported as revenue on a net basis in our consolidated statements of operations and comprehensive income (loss) because the purchases of inventory and subsequent sales of the inventory were with the same counterparty.

During the years ended December 31, 2018, 2017 and 2016, we generated the following transactions with related parties (in thousands):



	Year Ended December 31,
	2018		2017		2016
NGL Energy
Revenues	$	18,168	$	45,918	$	61,639
Purchases	$	681	$	29,695	$	57,739

White Cliffs
Crude oil revenues	$	—	$	436	$	4,973
Storage revenues	$	4,350	$	4,350	$	4,350
Transportation fees	$	12,506	$	11,298	$	10,797
Management fees	$	545	$	519	$	494
Crude oil purchases	$	6,201	$	11,870	$	4,758

Condensed Consolidating Guarantor Financial Statements

12 Months Ended

Dec. 31, 2018

Condensed Consolidating Guarantor Financial Statements [Abstract]

Condensed Financial Information of Parent Company Only Disclosure [Text Block]

CONDENSED CONSOLIDATING GUARANTOR FINANCIAL STATEMENTS

Our senior unsecured notes are guaranteed by certain of our subsidiaries as follows: Rose Rock Finance Corporation, Rose Rock Midstream Operating, LLC, Rose Rock Midstream Energy GP, LLC, Rose Rock Midstream Crude, L.P., Rose Rock Midstream Field Services, LLC, SemGas, L.P., SemMaterials, L.P., SemGroup Europe Holding, L.L.C., SemOperating G.P., L.L.C., SemMexico, L.L.C., SemDevelopment, L.L.C., Mid-America Midstream Gas Services, L.L.C., SemCrude Pipeline, L.L.C., and Wattenberg Holding, LLC (collectively, the “Guarantors”).

As of June 30, 2018, Beachhead Holdings LLC, Beachhead I LLC and Beachhead II LLC were added to the Guarantors and Glass Mountain Holding, LLC was removed as a guarantor. Accordingly, prior period financial information for 2017 below has been recast to reflect these changes. Financial information for 2016 was not recast due to immateriality.

Each of the Guarantors is 100% owned by SemGroup Corporation (the "Parent"). Such guarantees of the Notes are full and unconditional and constitute the joint and several obligations of the Guarantors. There are no significant restrictions upon the ability of the Parent or any of the Guarantors to obtain funds from its respective subsidiaries by dividend or loan. None of the assets of the Guarantors represent restricted net assets pursuant to Rule 4-08(e)(3) of Regulation S-X under the Securities Act.

Condensed consolidating financial statements for the Parent, the Guarantors and non-guarantors as of December 31, 2018 and 2017 and for the years ended December 31, 2018, 2017 and 2016 are presented on an equity method basis in the tables below (in thousands).

Intercompany receivable and payable balances, including notes receivable and payable, are capital transactions primarily to facilitate the capital needs of our subsidiaries. As such, subsidiary intercompany balances have been reported as a reduction to equity on the condensed consolidating Guarantor balance sheets. The Parent's net intercompany balance, including note receivable, and investments in subsidiaries have been reported in equity method investments on the condensed consolidating Guarantor balance sheets. Intercompany transactions, such as daily cash management activities, have been reported as financing activities within the condensed consolidating Guarantor statements of cash flows. The Parent's investing activities with subsidiaries have been reflected as cash flows from investing activities. These balances are eliminated through consolidating adjustments below.

Condensed Consolidating Guarantor Balance Sheets



	December 31, 2018
	Parent		Guarantors		Non-guarantors		Consolidating Adjustments			Consolidated
ASSETS
Current assets:
Cash and cash equivalents	$	40,064	$	—	$	50,742	$	(4,151	)	$	86,655
Accounts receivable	83		461,980		100,151		—			562,214
Receivable from affiliates	120		18		157		—			295
Inventories	—		49,397		—		—			49,397
Other current assets	6,682		6,711		3,871		—			17,264
Total current assets	46,949		518,106		154,921		(4,151		)	715,825
Property, plant and equipment	6,732		992,974		2,457,620		—			3,457,326
Equity method investments	3,267,581		1,553,360		—		(4,546,932		)	274,009
Goodwill	—		—		257,302		—			257,302
Other intangible assets	5		119,583		245,450		—			365,038
Other noncurrent assets, net	41,981		4,788		94,038		—			140,807
Total assets	$	3,363,248	$	3,188,811	$	3,209,331	$	(4,551,083	)	$	5,210,307
LIABILITIES, PREFERRED STOCK AND OWNERS’ EQUITY
Current liabilities:
Accounts payable	$	38	$	444,984	$	49,770	$	—		$	494,792
Payable to affiliates	1		3,714		—		—			3,715
Accrued liabilities	33,239		18,424		63,430		2			115,095
Other current liabilities	5,723		3,409		14,423		—			23,555
Total current liabilities	39,001		470,531		127,623		2			637,157
Long-term debt	1,467,083		6,315		811,751		(6,315		)	2,278,834
Deferred income taxes	4,882		—		50,907		—			55,789
Other noncurrent liabilities	1,792		—		36,756		—			38,548
Commitments and contingencies
Redeemable preferred stock	359,658		—		—		—			359,658
Owners' equity excluding noncontrolling interest in consolidated subsidiary	1,490,832		2,711,965		1,832,805		(4,544,770		)	1,490,832
Noncontrolling interest in consolidated subsidiary	—		—		349,489		—			349,489
Total owners’ equity	1,490,832		2,711,965		2,182,294		(4,544,770		)	1,840,321
Total liabilities, preferred stock and owners’ equity	$	3,363,248	$	3,188,811	$	3,209,331	$	(4,551,083	)	$	5,210,307



	December 31, 2017
	Parent			Guarantors		Non-guarantors		Consolidating Adjustments			Consolidated
ASSETS
Current assets:
Cash and cash equivalents	$	32,457		$	—	$	69,872	$	(8,630	)	$	93,699
Accounts receivable	(9		)	562,967		90,526		—			653,484
Receivable from affiliates	58			1,421		212		—			1,691
Current assets held for sale	—			—		38,063		—			38,063
Inventories	—			101,665		—		—			101,665
Other current assets	6,671			4,493		3,133		—			14,297
Total current assets	39,177			670,546		201,806		(8,630		)	902,899
Property, plant and equipment	8,086			1,002,982		2,304,063		—			3,315,131
Equity method investments	3,085,274			2,110,299		—		(4,910,292		)	285,281
Goodwill	—			—		257,302		—			257,302
Other intangible assets	10			127,783		270,850		—			398,643
Other noncurrent assets, net	45,587			3,097		83,916		—			132,600
Noncurrent assets held for sale	—			—		84,961		—			84,961
Total assets	$	3,178,134		$	3,914,707	$	3,202,898	$	(4,918,922	)	$	5,376,817
LIABILITIES AND OWNERS’ EQUITY
Current liabilities:
Accounts payable	$	646		$	533,651	$	53,601	$	—		$	587,898
Payable to affiliates	10			6,961		—		—			6,971
Accrued liabilities	38,747			26,092		66,570		(2		)	131,407
Current liabilities held for sale	—			—		23,847		—			23,847
Other current liabilities	1,922			5,532		8,984		—			16,438
Total current liabilities	41,325			572,236		153,002		(2		)	766,561
Long-term debt	1,474,491			572,558		829,236		(23,190		)	2,853,095
Deferred income taxes	1,892			—		44,693		—			46,585
Other noncurrent liabilities	2,061			—		36,434		—			38,495
Noncurrent liabilities held for sale	—			—		13,716		—			13,716
Commitments and contingencies
Total owners’ equity	1,658,365			2,769,913		2,125,817		(4,895,730		)	1,658,365
Total liabilities and owners’ equity	$	3,178,134		$	3,914,707	$	3,202,898	$	(4,918,922	)	$	5,376,817

Condensed Consolidating Guarantor Statements of Operations



	Year Ended December 31, 2018
	Parent			Guarantors			Non-guarantors			Consolidating Adjustments			Consolidated
Revenues:
Product	$	—		$	1,876,100		$	31,336		$	—		$	1,907,436
Service	—			140,275			378,489			—			518,764
Lease	—			—			17,549			—			17,549
Other	—			—			59,513			—			59,513
Total revenues	—			2,016,375			486,887			—			2,503,262
Expenses:
Costs of products sold, exclusive of depreciation and amortization shown below	—			1,796,716			26,379			—			1,823,095
Operating	—			110,795			173,974			—			284,769
General and administrative	23,580			24,742			43,246			—			91,568
Depreciation and amortization	2,890			76,788			129,576			—			209,254
Loss (gain) on disposal or impairment, net	133,053			(154,302		)	17,686			—			(3,563		)
Total expenses	159,523			1,854,739			390,861			—			2,405,123
Earnings from equity method investments	219,181			73,010			—			(234,519		)	57,672
Operating income	59,658			234,646			96,026			(234,519		)	155,811
Other expenses (income):
Interest expense	68,389			56,217			25,348			(240		)	149,714
Foreign currency transaction (gain) loss	10,246			147			(892		)	—			9,501
Other income, net	(976		)	(138		)	(1,506		)	240			(2,380		)
Total other expenses, net	77,659			56,226			22,950			—			156,835
Income (loss) from continuing operations before income taxes	(18,001		)	178,420			73,076			(234,519		)	(1,024		)
Income tax expense	8,748			—			14,556			—			23,304
Net income (loss)	(26,749		)	178,420			58,520			(234,519		)	(24,328		)
Less: net income attributable to noncontrolling interest	—			—			2,421			—			2,421
Net income (loss) attributable to SemGroup	(26,749		)	178,420			56,099			(234,519		)	(26,749		)
Less: cumulative preferred stock dividends	23,790			—			—			—			23,790
Net income (loss) attributable to common shareholders	$	(50,539	)	$	178,420		$	56,099		$	(234,519	)	$	(50,539	)
Net income (loss)	$	(26,749	)	$	178,420		$	58,520		$	(234,519	)	$	(24,328	)
Other comprehensive income (loss), net of income taxes	(9,420		)	387			11,587			—			2,554
Comprehensive income (loss)	(36,169		)	178,807			70,107			(234,519		)	(21,774		)
Less: comprehensive income attributable to noncontrolling interest	—			—			2,421			—			2,421
Comprehensive income (loss) attributable to SemGroup	$	(36,169	)	$	178,807		$	67,686		$	(234,519	)	$	(24,195	)



	Year Ended December 31, 2017
	Parent			Guarantors			Non-guarantors			Consolidating Adjustments			Consolidated
Revenues:
Product	$	—		$	1,468,754		$	153,164		$	—		$	1,621,918
Service	—			149,197			242,069			—			391,266
Lease	—			—			5,843			—			5,843
Other	—			—			62,890			—			62,890
Total revenues	—			1,617,951			463,966			—			2,081,917
Expenses:
Costs of products sold, exclusive of depreciation and amortization shown below	—			1,383,868			131,023			—			1,514,891
Operating	—			112,863			141,901			—			254,764
General and administrative	42,422			24,492			46,865			—			113,779
Depreciation and amortization	2,294			70,053			86,074			—			158,421
Loss (gain) on disposal or impairment, net	—			70,681			(57,348		)	—			13,333
Total expenses	44,716			1,661,957			348,515			—			2,055,188
Earnings from equity method investments	68,964			(21,499		)	7,494			12,372			67,331
Operating income (loss)	24,248			(65,505		)	122,945			12,372			94,060
Other expenses (income):
Interest expense	40,053			55,119			8,691			(854		)	103,009
Loss on early extinguishment of debt	19,930			—			—			—			19,930
Foreign currency transaction gain	(2,764		)	—			(1,945		)	—			(4,709		)
Other income, net	(913		)	(33		)	(4,540		)	854			(4,632		)
Total other expenses, net	56,306			55,086			2,206			—			113,598
Income (loss) from continuing operations before income taxes	(32,058		)	(120,591		)	120,739			12,372			(19,538		)
Income tax expense (benefit)	(14,908		)	—			12,520			—			(2,388		)
Income (loss) from continuing operations	(17,150		)	(120,591		)	108,219			12,372			(17,150		)
Net income (loss)	$	(17,150	)	$	(120,591	)	$	108,219		$	12,372		$	(17,150	)
Net income (loss)	$	(17,150	)	$	(120,591	)	$	108,219		$	12,372		$	(17,150	)
Other comprehensive income (loss), net of income taxes	(11,987		)	(573		)	32,673			—			20,113
Comprehensive income (loss)	$	(29,137	)	$	(121,164	)	$	140,892		$	12,372		$	2,963



	Year Ended December 31, 2016
	Parent			Guarantors		Non-guarantors			Consolidating Adjustments			Consolidated
Revenues:
Product	$	—		$	872,961	$	136,448		$	—		$	1,009,409
Service	—			162,460		102,570			—			265,030
Other	—			—		57,725			—			57,725
Total revenues	—			1,035,421		296,743			—			1,332,164
Expenses:
Costs of products sold, exclusive of depreciation and amortization shown below	—			761,971		111,460			—			873,431
Operating	—			115,431		96,668			—			212,099
General and administrative	22,349			31,196		30,638			—			84,183
Depreciation and amortization	1,647			68,669		28,488			—			98,804
Loss (gain) on disposal or impairment, net	—			16,115		(67		)	—			16,048
Total expenses	23,996			993,382		267,187			—			1,284,565
Earnings from equity method investments	56,815			81,366		—			(64,424		)	73,757
Loss on issuance of common units by equity method investee	(41		)	—		—			—			(41		)
Operating income	32,778			123,405		29,556			(64,424		)	121,315
Other expenses (income):
Interest expense (income)	(4,002		)	72,277		(4,819		)	(806		)	62,650
Foreign currency transaction loss	—			—		4,759			—			4,759
Loss on sale or impairment of non-operated equity method investment, net	30,644			—		—			—			30,644
Other expenses (income), net	(339		)	63		(1,799		)	806			(1,269		)
Total other expenses (income), net	26,303			72,340		(1,859		)	—			96,784
Income from continuing operations before income taxes	6,475			51,065		31,415			(64,424		)	24,531
Income tax expense	4,380			—		6,888			—			11,268
Income from continuing operations	2,095			51,065		24,527			(64,424		)	13,263
Loss from discontinued operations, net of income taxes	—			—		(1		)	—			(1		)
Net income	2,095			51,065		24,526			(64,424		)	13,262
Less: net income attributable to noncontrolling interests	—			11,167		—			—			11,167
Net income attributable to SemGroup	$	2,095		$	39,898	$	24,526		$	(64,424	)	$	2,095
Net income	$	2,095		$	51,065	$	24,526		$	(64,424	)	$	13,262
Other comprehensive income (loss), net of income taxes	7,360			1,223		(23,935		)	—			(15,352		)
Comprehensive income (loss)	9,455			52,288		591			(64,424		)	(2,090		)
Less: comprehensive income attributable to noncontrolling interests	—			11,167		—			—			11,167
Comprehensive income (loss) attributable to SemGroup	$	9,455		$	41,121	$	591		$	(64,424	)	$	(13,257	)

Condensed Consolidating Guarantor Statements of Cash Flows



	Year Ended December 31, 2018
	Parent			Guarantors			Non-guarantors			Consolidating Adjustments			Consolidated
Net cash provided by (used in) operating activities	$	(90,572	)	$	144,902		$	215,374		$	—		$	269,704
Cash flows from investing activities:
Capital expenditures	(1,529		)	(65,798		)	(323,407		)	—			(390,734		)
Proceeds from sale of equity method investment and other long-lived assets	—			664			1,294			—			1,958
Contributions to equity method investments	—			(7,781		)	—			—			(7,781		)
Proceeds from business divestitures	156,499			6,753			(15,465		)	—			147,787
Distributions from equity method investees in excess of equity in earnings	—			19,100			—			—			19,100
Net cash provided by (used in) investing activities	154,970			(47,062		)	(337,578		)	—			(229,670		)
Cash flows from financing activities:
Debt issuance costs	(475		)	—			(4,245		)	—			(4,720		)
Borrowings on credit facilities and issuance of senior unsecured notes	660,000			—			598,500			—			1,258,500
Principal payments on credit facilities and other obligations	(678,865		)	(565,904		)	(595,125		)	—			(1,839,894		)
Equity issuance to noncontrolling interest	350,000			—			—			—			350,000
Distributions to noncontrolling interests	(2,932		)	—			—			—			(2,932		)
Proceeds from preferred stock issuance, net of offering costs	342,299			—			—			—			342,299
Repurchase of common stock for payment of statutory taxes due on equity-based compensation	(705		)	—			—			—			(705		)
Dividends paid	(148,482		)	—			—			—			(148,482		)
Proceeds from issuance of common stock under employee stock purchase plan	930			—			—			—			930
Intercompany borrowings (advances), net	(578,561		)	468,079			106,003			4,479			—
Net cash provided by (used in) financing activities	(56,791		)	(97,825		)	105,133			4,479			(45,004		)
Effect of exchange rate changes on cash and cash equivalents	—			(15		)	(2,059		)	—			(2,074		)
Change in cash and cash equivalents	7,607			—			(19,130		)	4,479			(7,044		)
Cash and cash equivalents at beginning of period	32,457			—			69,872			(8,630		)	93,699
Cash and cash equivalents at end of period	$	40,064		$	—		$	50,742		$	(4,151	)	$	86,655



	Year Ended December 31, 2017
	Parent			Guarantors			Non-guarantors			Consolidating Adjustments			Consolidated
Net cash provided by (used in) operating activities	$	(46,556	)	$	93,107		$	93,925		$	—		$	140,476
Cash flows from investing activities:
Capital expenditures	(4,554		)	(135,999		)	(322,160		)	—			(462,713		)
Proceeds from sale of long-lived assets	—			15,565			299,256			—			314,821
Contributions to equity method investments	—			(2,888		)	(23,556		)	—			(26,444		)
Payments to acquire business, net of cash acquired	—			—			(294,239		)	—			(294,239		)
Distributions from equity method investments in excess of equity in earnings	—			18,261			10,513			—			28,774
Net cash provided by (used in) investing activities	(4,554		)	(105,061		)	(330,186		)	—			(439,801		)
Cash flows from financing activities:
Debt issuance costs	(11,116		)	—			—			—			(11,116		)
Borrowings on credit facilities and issuance of senior unsecured notes	1,470,377			—			55,000			—			1,525,377
Principal payments on debt and other obligations	(1,049,652		)	(26		)	(2,750		)	—			(1,052,428		)
Debt extinguishment costs	(16,293		)	—			—			—			(16,293		)
Repurchase of common stock	(1,473		)	—			—			—			(1,473		)
Dividends paid	(129,925		)	—			—			—			(129,925		)
Proceeds from issuance of common stock under employee stock purchase plan	1,114			—			—			—			1,114
Intercompany borrowings (advances), net	(198,467		)	11,980			190,535			(4,048		)	—
Net cash provided by (used in) financing activities	64,565			11,954			242,785			(4,048		)	315,256
Effect of exchange rate changes on cash and cash equivalents	—			—			3,552			—			3,552
Change in cash and cash equivalents	13,455			—			10,076			(4,048		)	19,483
Cash and cash equivalents at beginning of period	19,002			—			59,796			(4,582		)	74,216
Cash and cash equivalents at end of period	$	32,457		$	—		$	69,872		$	(8,630	)	$	93,699



	Year Ended December 31, 2016
	Parent			Guarantors			Non-guarantors			Consolidating Adjustments			Consolidated
Net cash provided by operating activities	$	84,460		$	79,054		$	65,282		$	(58,822	)	$	169,974
Cash flows from investing activities:
Capital expenditures	(2,928		)	(56,102		)	(253,426		)	—			(312,456		)
Proceeds from sale of long-lived assets	—			53			98			—			151
Contributions to equity method investments	—			(4,188		)	—			—			(4,188		)
Proceeds from sale of common units of equity method investee	60,483			—			—			—			60,483
Distributions from equity method investments in excess of equity in earnings	—			27,726			—			—			27,726
Net cash provided by (used in) investing activities	57,555			(32,511		)	(253,328		)	—			(228,284		)
Cash flows from financing activities:
Debt issuance costs	(7,728		)	—			—			—			(7,728		)
Borrowings on credit facilities and issuance of senior unsecured notes	382,500			—			—			—			382,500
Principal payments on credit facilities and other obligations	(396,859		)	(31		)	—			—			(396,890		)
Distributions to noncontrolling interests	—			(32,133		)	—			—			(32,133		)
Proceeds from issuance of common shares, net of offering costs	223,025			—			—			—			223,025
Repurchase of common stock	(965		)	—			—			—			(965		)
Dividends paid	(92,910		)	—			—			—			(92,910		)
Proceeds from issuance of common stock under employee stock purchase plan	1,010			—			—			—			1,010
Intercompany borrowings (advances), net	(235,645		)	(23,437		)	203,278			55,804			—
Net cash provided by (used in) financing activities	(127,572		)	(55,601		)	203,278			55,804			75,909
Effect of exchange rate changes on cash and cash equivalents	—			—			(1,479		)	—			(1,479		)
Change in cash and cash equivalents	14,443			(9,058		)	13,753			(3,018		)	16,120
Cash and cash equivalents at beginning of period	4,559			9,058			46,043			(1,564		)	58,096
Cash and cash equivalents at end of period	$	19,002		$	—		$	59,796		$	(4,582	)	$	74,216

Subsequent Events (Notes)	12 Months Ended
Subsequent Events (Notes)	Dec. 31, 2018
Subsequent Events [Abstract]
Subsequent Events [Text Block]	26. SUBSEQUENT EVENTS SemCAMS Midstream On January 9, 2019, a wholly owned subsidiary of SemGroup Corporation, SemCanada II, L.P., an Oklahoma limited partnership (“SemGroup”), and an affiliate of Kohlberg Kravis Roberts & Co. L.P. and wholly owned subsidiary of KKR Global Infrastructure Investors III L.P., KKR Alberta Midstream Inc., an Alberta corporation (“KKR”), entered into definitive documents to create a new joint venture company that will own and operate midstream oil and gas infrastructure in Western Canada, SemCAMS Midstream ULC, an Alberta unlimited liability corporation (“SemCAMS Midstream”). SemGroup owns 51% and KKR owns 49% of SemCAMS Midstream, subsequent to close of the transactions described below. Share Purchase Agreement In connection with the formation of SemCAMS Midstream, on January 9, 2019, SemCAMS Midstream entered into a Share Purchase Agreement (the “Share Purchase Agreement”) with Meritage Midstream Services III, LP (“Meritage”) to acquire 100% of the issued and outstanding equity interests in Meritage Midstream ULC, an Alberta unlimited liability corporation (“Meritage ULC” and such acquisition, the “Meritage Acquisition”). On February 25, 2019, SemCAMS Midstream completed the Meritage Acquisition pursuant to the Share Purchase Agreement for a debt-free, cash purchase price of C$646.5 million (US$489.5 million), subject to customary post-closing adjustments. The purchase price included C$152.3 million (US$115.5 million) in reimbursements for estimated capital expenditures incurred from September 1, 2018 to the closing of the Meritage Acquisition (the “Meritage Closing”). Pursuant to the Share Purchase Agreement, SemCAMS Midstream has obtained a representation and warranty insurance policy to cover losses arising from breaches of representations and warranties by Meritage. Each party has agreed to indemnify the other for breaches of covenants and certain other matters, subject to certain exceptions and limitations. Investment and Contribution Agreement Concurrently with the execution of the Share Purchase Agreement, SemGroup, KKR and SemCAMS Midstream entered into an Investment and Contribution Agreement (the “Contribution Agreement”). On February 25, 2019, the Contribution (as defined below) closed immediately prior to the Meritage Closing (the “Contribution Closing”). Pursuant to the terms of the Contribution Agreement, each of SemGroup and KKR made the following contributions to SemCAMS Midstream: (i) SemGroup contributed 100% of the issued and outstanding equity interests in its wholly owned subsidiary, SemCAMS ULC, an Alberta unlimited liability company, (the “SemGroup Contribution”) in exchange for (A) 51% of the common shares of SemCAMS Midstream, (B) a cash amount of C$645.6 million (US$489.6 million), subject to adjustments for working capital of SemCAMS ULC, capital contributions to SemCAMS ULC by SemGroup, and other customary adjustments, (C) a potential payment of C$14.7 million (US$11.1 million) contingent on positive final investment decision of a specific project by SemCAMS Midstream, and (D) earnout consideration in the form of a special share in SemCAMS Midstream entitled to dividend payments up to a maximum (pre-tax) aggregate amount of C$50.0 million (US$37.9 million) if either or both of two specific projects proceed and EBITDA thresholds pertaining to those projects are achieved; and (ii) KKR contributed cash in the amount of C$785.6 million (US$595.7 million), subject to adjustments for working capital of SemCAMS ULC, capital contributions to SemCAMS ULC by SemGroup and a payment of C$14.7 million (US$11.1 million) contingent on the pursuit of a specific project (unrelated to the two projects referred to above) by SemCAMS Midstream, and other customary adjustments (the “KKR Contribution” and, together with the SemGroup Contribution, the “Contribution”) in exchange for (A) 49% of the common shares of SemCAMS Midstream and (B) 300,000 preferred shares in SemCAMS Midstream (representing C$300 million (US$227.5 million) of KKR cash contribution) which will pay quarterly dividends at an annual rate of 8.75%. SemCAMS Midstream may elect, for any of the first ten quarters following issuance of the preferred shares, to pay the dividends in-kind in the form of additional preferred shares. SemCAMS Midstream will have the right to convert the preferred shares into common shares in the event of an initial public offering of its common shares, at a conversion price equal to 92.5% of the IPO offering price. In connection with the issuance of the preferred shares, KKR received a C$6.0 million (US$4.5 million) transaction fee from SemCAMS Midstream. KKR and SemGroup have agreed to indemnify each other for breaches of covenants and certain other matters, subject to certain exceptions and limitations. Upon the Contribution Closing, KKR and SemGroup entered into a unanimous shareholder agreement (the “Shareholder Agreement”) to cover corporate governance, transfer restrictions, funding obligations and other similar matters related to SemCAMS Midstream. The Shareholder Agreement includes customary restrictions on the activities of SemGroup and KKR that relate to the business of SemCAMS Midstream within a defined area of mutual interest surrounding the location in which SemCAMS Midstream will operate. In addition, the Shareholder Agreement includes certain liquidity rights that allow each of KKR and SemGroup to cause SemCAMS Midstream to pursue an initial public offering of its respective common shares after the third anniversary of the parties’ entry into the Shareholder Agreement.

Consolidation and Basis of Presentation (Policies)	12 Months Ended
Consolidation and Basis of Presentation (Policies)	Dec. 31, 2018
Policy Text Block [Abstract]
Consolidation, Policy [Policy Text Block]	Consolidated subsidiaries Our consolidated financial statements include the accounts of our controlled subsidiaries. All significant transactions between our consolidated subsidiaries have been eliminated. Outside ownership interests in consolidated subsidiaries are reported as noncontrolling interests in the consolidated financial statements. Proportionally consolidated assets Our Canada segment owns undivided interests in certain natural gas gathering and processing assets, for which we record only our proportionate share of the assets on the consolidated balance sheets. The net book value of the property, plant and equipment recorded by us associated with these undivided interests is approximately $570.8 million at December 31, 2018. We serve as operator of these facilities and incur the costs of operating the facilities (recorded as operating expenses in the consolidated statements of operations) and charge the other owners, which are also customers, for their proportionate share of the costs (recorded as other revenue in the consolidated statements of operations). Equity method investments We own a 51% interest in White Cliffs Pipeline, LLC ("White Cliffs"), which we account for under the equity method as the other owners have substantive rights to participate in its management. White Cliffs is included in our U.S. Liquids segment. We own an 11.78% interest in the general partner of NGL Energy Partners LP (NYSE: NGL) ("NGL Energy") which we account for under the equity method. Our investment in NGL Energy is included in Corporate and Other for segment reporting.

Summary of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2018

Accounting Policies [Abstract]

Use of Estimates

Cash And Cash Equivalents

Accounts Receivable

ACCOUNTS RECEIVABLE—Accounts receivable are reported net of the allowance for doubtful accounts. Our assessment of the allowance for doubtful accounts is based on several factors, including the overall creditworthiness of our customers, existing economic conditions, and the amount and age of past due accounts. We enter into netting arrangements with certain counterparties to help mitigate credit risk. Receivables subject to netting are presented as gross receivables (with the related accounts payable also presented gross) until such time as the balances are settled. Receivables are considered past due if full payment is not received by the contractual due date. Past due accounts are written off against the allowance for doubtful accounts only after all collection attempts have been exhausted.In June 2016, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update ("ASU") 2016-13, "Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments", which introduces new guidance for estimating credit losses on certain types of financial instruments based on expected losses and the timing of the recognition of such losses. For public entities, this ASU is effective for annual periods beginning after December 15, 2019, and interim periods within those years and early adoption is permitted in the year prior to the effective date. We will adopt this guidance in the first quarter of 2020. The impact is not expected to be material.

Inventories

Property, Plant and Equipment

Depreciation is calculated primarily using the straight-line method over the following estimated useful lives:



Pipelines and related facilities	10 – 31 years
Storage and terminal facilities	10 – 25 years
Natural gas gathering and processing facilities	10 – 31 years
Trucking equipment and other	3 – 7 years
Office property and equipment	3 – 31 years

Construction in process is reclassified to the fixed asset categories above and depreciation commences once the asset has been placed in-service.

Linefill

LINEFILL—Pipelines and storage facilities generally require a minimum volume of product in the system to enable the system to operate. Such product, known as linefill, is generally not available to be withdrawn from the system. Linefill owned by us in facilities operated by us is recorded at historical cost, is included in property, plant and equipment in the consolidated balance sheets, and is not depreciated. We also own linefill in third-party facilities, which is included in inventory on the consolidated balance sheets.

Impairment of Long-Lived Assets

Goodwill

Intangible Assets

Equity Method Investments

Debt Issuance Costs

Commodity Derivative Instruments

Contingent Losses

Asset Retirement Obligations

Stockholders' Equity Note, Redeemable Preferred Stock, Issue, Policy [Policy Text Block]

Revenue Recognition



	December 31, 2018
	Under ASC 606			Under ASC 605			Increase/(Decrease)
Accounts receivable, net	$	562,214		$	562,057		$	157
Other noncurrent assets	$	140,807		$	119,911		$	20,896
Other current liabilities	$	6,495		$	6,538		$	(43	)
Deferred income taxes	$	55,789		$	50,045		$	5,744
Accumulated deficit	$	(73,971	)	$	(89,324	)	$	15,353



	Year Ended December 31, 2018
	Under ASC 606			Under ASC 605			Increase/(Decrease)
Revenue	$	2,503,262		$	2,483,962		$	19,300
Cost of sales	$	1,823,095		$	1,808,129		$	14,966
General and administrative expense	$	91,568		$	91,168		$	400
Income tax benefit	$	23,304		$	23,209		$	95
Net loss	$	(24,328	)	$	(28,167	)	$	3,839



Net loss attributable to common shareholders	$	(50,539	)	$	(54,378	)	$	3,839
Net loss per common share:
Basic	$	(0.65	)	$	(0.70	)	$	0.05
Diluted	$	(0.65	)	$	(0.70	)	$	0.05

•


•	Changes to cost of sales are due to how certain gathering and processing fees related to percentage of proceeds contracts are treated as revenues rather than reductions to purchase price of commodities (cost of sales).

•


•	Changes to other noncurrent assets include success fee payments to third parties for certain contracts which were expensed as incurred under ASC 605, but which have been recognized as assets under ASC 606 and are amortized to general and administrative expense in the consolidated statement of operations and comprehensive income (loss).


•	Changes to deferred income taxes primarily relate to the deferred tax impact of adoption entries.


•	Changes to retained earnings are due to the impact of adoption at January 1, 2018, as described above, and cumulative differences in net income through December 31, 2018.

See Note 18 for additional information.

Costs of Products Sold

Purchases and Sales of Inventory With the Same Counterparty

Currency Translation

Income Taxes

Reclassifications

RECLASSIFICATIONS—Certain reclassifications have been made to conform prior year balances to the current year presentation.

Pension Benefits

PENSION BENEFITS—Pension cost and obligations are actuarially determined and are affected by assumptions including expected return on plan assets, discount rates, compensation increases, and employee turnover rates. We evaluate our assumptions periodically and make adjustments to these assumptions and the recorded liability as necessary. Actuarial gains or losses are amortized on a straight-line basis over the expected remaining service life of employees in the pension plan.In March 2017, the FASB issued ASU 2017-07, “Compensation - Retirement Benefits (Topic 715): Improving the Presentation of Net Periodic Pension Cost and Net Periodic Post-retirement Benefit Cost”, which requires that an employer disaggregate the service cost component from other components of net benefit cost. This ASU also provides explicit guidance on how to present the service cost component and the other components of net benefit cost in the income statement and allows only the service cost component of net benefit cost to be eligible for capitalization. We adopted this guidance retrospectively in the first quarter of 2018. For the years ended December 31, 2017 and 2016, we reclassified $3.2 million, of non-service pension gains and $0.3 million of non-service pension costs, respectively, from “general and administrative expense” to “other expense (income)”.

Equity-Based Compensation

EQUITY-BASED COMPENSATION—We grant certain of our employees and non-managerial directors equity-based compensation awards which vest contingent on continued service of the recipient and, in some cases, on their achievement of specific performance targets or market conditions. We record compensation expense for these outstanding awards over applicable service or performance periods based on their grant date fair value with a corresponding increase to additional paid-in capital. In May 2017, the FASB issued ASU 2017-09, “Compensation - Stock Compensation (Topic 718): Scope of Modification Accounting”, to provide clarity and reduce diversity in practice in determining which changes to terms or conditions of a share-based payment award require an entity to apply modification accounting under Accounting Standards Codification Topic 718. We adopted this guidance in the first quarter of 2018. The impact was not material.

Consolidation, Subsidiaries or Other Investments, Consolidated Entities, Policy [Policy Text Block]

Comprehensive Income

New Accounting Pronouncements, Policy [Policy Text Block]

Financial Instruments and Concentrations of Risk Financial Instruments (Policies)	12 Months Ended
	Dec. 31, 2018
Financial Instruments Policies [Abstract]
Fair Value Measurement, Policy [Policy Text Block]	“Level 1” measurements are based on inputs consisting of unadjusted quoted prices in active markets that are accessible at the measurement date for identical, unrestricted assets or liabilities. These include commodity futures contracts that are traded on an exchange. “Level 2” measurements are based on inputs consisting of market observable and corroborated prices for similar derivative contracts. Assets and liabilities classified as Level 2 include over the counter (“OTC”) traded physical fixed priced purchases and sales forward contracts. “Level 3” measurements are based on inputs from a pricing service and/or internal valuation models incorporating observable and unobservable market data. These could include commodity derivatives, such as forwards and swaps for which there is not a highly liquid market and therefore are not included in Level 2 above and interest rate swaps for which certain unobservable inputs are used in the valuation. Financial assets and liabilities are classified based on the lowest level of input that is significant to the fair value measurement. Our assessment of the significance of a particular input to the measurement requires judgment and may affect the valuation of assets and liabilities and their placement within the fair value levels. At December 31, 2018, all of our physical fixed price forward purchases and sales contracts were being accounted for as normal purchases and normal sales.

Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2018

Property, Plant and Equipment [Line Items]

Schedule of New Accounting Pronouncements and Changes in Accounting Principles [Table Text Block]

The impacts of adoption to the current period results are as follows (in thousands):



	December 31, 2018
	Under ASC 606			Under ASC 605			Increase/(Decrease)
Accounts receivable, net	$	562,214		$	562,057		$	157
Other noncurrent assets	$	140,807		$	119,911		$	20,896
Other current liabilities	$	6,495		$	6,538		$	(43	)
Deferred income taxes	$	55,789		$	50,045		$	5,744
Accumulated deficit	$	(73,971	)	$	(89,324	)	$	15,353



	Year Ended December 31, 2018
	Under ASC 606			Under ASC 605			Increase/(Decrease)
Revenue	$	2,503,262		$	2,483,962		$	19,300
Cost of sales	$	1,823,095		$	1,808,129		$	14,966
General and administrative expense	$	91,568		$	91,168		$	400
Income tax benefit	$	23,304		$	23,209		$	95
Net loss	$	(24,328	)	$	(28,167	)	$	3,839



Net loss attributable to common shareholders	$	(50,539	)	$	(54,378	)	$	3,839
Net loss per common share:
Basic	$	(0.65	)	$	(0.70	)	$	0.05
Diluted	$	(0.65	)	$	(0.70	)	$	0.05

Property, Plant and Equipment [Table Text Block]

Depreciation is calculated primarily using the straight-line method over the following estimated useful lives:



Pipelines and related facilities	10 – 31 years
Storage and terminal facilities	10 – 25 years
Natural gas gathering and processing facilities	10 – 31 years
Trucking equipment and other	3 – 7 years
Office property and equipment	3 – 31 years

Property, plant and equipment consists of the following (in thousands):



	December 31,
	2018			2017
Land	$	308,166		$	273,168
Pipelines and related facilities	1,023,502			926,799
Storage and terminal facilities	1,247,115			1,111,001
Natural gas gathering and processing facilities	1,055,305			940,130
Linefill	27,972			25,747
Trucking equipment and other	45,567			45,162
Office property and equipment	69,498			63,052
Construction-in-progress	288,104			374,914
Property, plant and equipment, gross	4,065,229			3,759,973
Accumulated depreciation	(607,903		)	(444,842		)
Property, plant and equipment, net	$	3,457,326		$	3,315,131

Disposals of Long-Lived Assets (Tables)

12 Months Ended

Dec. 31, 2018

Disposals And Impairments Of Long-Lived Assets [Abstract]

Disposal Groups, Including Discontinued Operations [Table Text Block]



	Segment	Loss/(Gain)
Write-down of Mexican asphalt business to net realizable value	Corporate and Other	$	13,511
Write-down U.K. operations to net realizable value	Corporate and Other	76,661
Sherman natural gas gathering and processing asset impairment	U.S. Gas	30,985
Crude oil trucking goodwill impairment (Note 9)	U.S. Liquids	26,628
Crude oil trucking intangible asset impairment (Note 9)	U.S. Liquids	12,087
Gain on sale of Glass Mountain Pipeline LLC (Note 6)	U.S. Liquids	(150,266		)
Other		3,727
Loss on disposal or impairment, net		$	13,333

- Definition

Tabular disclosure of information related to a disposal group. Includes, but is not limited to, a discontinued operation, disposal classified as held-for-sale or disposed of by means other than sale or disposal of an individually significant component.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 50
-Paragraph 3A
-URI http://asc.fasb.org/extlink&oid=109226691&loc=SL51724579-110230

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 20
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=109222650&loc=d3e1474-107760

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 20
-Section 50
-Paragraph 5D
-URI http://asc.fasb.org/extlink&oid=109222650&loc=SL51721677-107760

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 20
-Section 45
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=109222160&loc=SL51721533-107759

Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 20
-Section 50
-Paragraph 3A
-URI http://asc.fasb.org/extlink&oid=109222650&loc=SL51721659-107760

Reference 6: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 20
-Section 50
-Paragraph 4B
-URI http://asc.fasb.org/extlink&oid=109222650&loc=SL51721665-107760

Reference 7: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=109226691&loc=d3e2941-110230

Reference 8: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 20
-Section 50
-Paragraph 5C
-URI http://asc.fasb.org/extlink&oid=109222650&loc=SL51721675-107760

Reference 9: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 20
-Section 50
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=109222650&loc=SL51721683-107760

Reference 10: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 20
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=109222650&loc=d3e1361-107760

Reference 11: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 20
-Section 50
-Paragraph 5A
-URI http://asc.fasb.org/extlink&oid=109222650&loc=SL51721671-107760

Reference 12: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 20
-Section 50
-Paragraph 5B
-URI http://asc.fasb.org/extlink&oid=109222650&loc=SL51721673-107760

Reference 13: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 20
-Section 50
-Paragraph 4A
-URI http://asc.fasb.org/extlink&oid=109222650&loc=SL51721663-107760

+ Details

Equity Method Investments (Tables)

12 Months Ended

Dec. 31, 2018

Equity Method Investments [Table Text Block]

Our earnings from equity method investments consist of the following (in thousands):



	Year Ended December 31,
	2018		2017			2016
White Cliffs	$	57,625	$	59,851		$	69,007
Glass Mountain	—		7,494			2,562
NGL Energy⁽¹⁾	47		(14		)	2,188
Total earnings from equity method investments	$	57,672	$	67,331		$	73,757

(1) Excluding a loss on issuance of common units of $41.0 thousand for the year ended December 31, 2016Cash distributions received from equity method investments consist of the following (in thousands):



	Year Ended December 31,
	2018		2017		2016
White Cliffs	$	76,725	$	77,511	$	88,839
Glass Mountain	—		18,011		10,456
NGL Energy	—		—		4,873
Total cash distributions received from equity method investments	$	76,725	$	95,522	$	104,168

Our equity method investments consist of the following (in thousands):



	December 31,
	2018		2017
White Cliffs	$	255,043	$	266,362
NGL Energy	18,966		18,919
Total equity method investments	$	274,009	$	285,281

Other Assets (Tables)

12 Months Ended

Dec. 31, 2018

Other Assets [Abstract]

Other current assets

Other current assets consist of the following (in thousands):



	December 31,
	2018		2017
Prepaid expenses	$	8,379	$	8,746
Other	8,885		5,551
Total other current assets	$	17,264	$	14,297

Other noncurrent assets

Other noncurrent assets consist of the following (in thousands):



	December 31,
	2018		2017
Capitalized loan fees	$	6,074	$	8,774
Net investment in direct financing lease	69,222		67,825
Deferred tax asset	25,307		33,792
Other	40,204		22,209
Total other noncurrent assets, net	$	140,807	$	132,600

Direct Financing Lease, Future Minimum Payments Receivable [Table Text Block]

At December 31, 2018, minimum lease payments to be received for each of the five succeeding fiscal years and thereafter are as follows (in thousands):



For the year ending:
December 31, 2019	$	13,732
December 31, 2020	13,031
December 31, 2021	12,800
December 31, 2022	12,804
December 31, 2023	12,808
Thereafter	18,151
Total minimum lease payments	$	83,326

Property, Plant and Equipment (Tables)

12 Months Ended

Dec. 31, 2018

Property, Plant and Equipment [Abstract]

Property, Plant and Equipment [Table Text Block]

Depreciation is calculated primarily using the straight-line method over the following estimated useful lives:



Pipelines and related facilities	10 – 31 years
Storage and terminal facilities	10 – 25 years
Natural gas gathering and processing facilities	10 – 31 years
Trucking equipment and other	3 – 7 years
Office property and equipment	3 – 31 years

Property, plant and equipment consists of the following (in thousands):



	December 31,
	2018			2017
Land	$	308,166		$	273,168
Pipelines and related facilities	1,023,502			926,799
Storage and terminal facilities	1,247,115			1,111,001
Natural gas gathering and processing facilities	1,055,305			940,130
Linefill	27,972			25,747
Trucking equipment and other	45,567			45,162
Office property and equipment	69,498			63,052
Construction-in-progress	288,104			374,914
Property, plant and equipment, gross	4,065,229			3,759,973
Accumulated depreciation	(607,903		)	(444,842		)
Property, plant and equipment, net	$	3,457,326		$	3,315,131

Goodwill and Other Intangible Assets (Tables)

12 Months Ended

Dec. 31, 2018

Goodwill And Other Intangible Assets [Abstract]

Schedule of Goodwill [Table Text Block]

Changes in goodwill balances during the period from December 31, 2015 to December 31, 2018 are shown below (in thousands):



Balance, December 31, 2015	$	48,032
U.S. Gas impairment loss	(13,052		)
Currency translation adjustments	(750		)
Balance, December 31, 2016	34,230
U.S. Liquids - Crude oil trucking impairment loss	(26,628		)
Reclassification of Mexican asphalt business goodwill as held for sale (Note 4)	(7,808		)
U.S. Liquids - HFOTCO acquisition (Note 5)	257,302
Currency translation adjustments	206
Balance, December 31, 2017	257,302
Balance, December 31, 2018	$	257,302

Schedule of Other Intangible Assets

The gross carrying amount and accumulated amortization of intangible assets are shown below (in thousands):



	December 31, 2018							December 31, 2017
	Gross Carrying Amount		Accumulated Amortization			Net Carrying Amount		Gross Carrying Amount		Accumulated Amortization			Net Carrying Amount
Customer relationships	$	424,000	$	(67,917	)	$	356,083	$	424,000	$	(49,717	)	$	374,283
Non-compete agreement	30,000		(21,250		)	8,750		30,000		(6,250		)	23,750
Trade names	52		(47		)	5		52		(42		)	10
Customer contract	1,000		(800		)	200		1,000		(400		)	600
Total other intangible assets	$	455,052	$	(90,014	)	$	365,038	$	455,052	$	(56,409	)	$	398,643

Changes in other intangible asset balances during the period from December 31, 2015 to December 31, 2018, are shown below (in thousands):



Balance, December 31, 2015	$	162,223
Amortization	(10,928		)
Currency translation adjustments	(317		)
Balance, December 31, 2016	150,978
U.S. Liquids - HFOTCO acquisition (Note 5)	291,000
U.S. Liquids - Crude oil trucking impairment	(12,087		)
Reclassification of Mexican asphalt assets as held for sale (Note 4)	(715		)
Amortization	(30,628		)
Currency translation adjustments	95
Balance, December 31, 2017	398,643
Amortization	(33,605		)
Balance, December 31, 2018	$	365,038

Future Amortization of Other Intangible Assets

We estimate that future amortization of other intangible assets will be as follows (in thousands):



For the year ending:
December 31, 2019	$	39,455
December 31, 2020	30,000
December 31, 2021	30,200
December 31, 2022	28,600
December 31, 2023	27,100
Thereafter	209,683
Total estimated amortization expense	$	365,038

Financial Instruments and Concentrations of Risk (Tables)

12 Months Ended

Dec. 31, 2018

Fair Value Disclosures [Abstract]

Fair Value of Financial Assets and Liabilities

The table below summarizes the balances of commodity derivative assets and liabilities at December 31, 2018 and 2017 (in thousands):



	December 31, 2018
	Level 1			Level 2			Level 3			Netting⁽¹⁾			Total
Assets:
Commodity derivatives ⁽²⁾	$	4,658		$	—		$	—		$	(973	)	$	3,685
Total assets	4,658			—			—			(973		)	3,685
Liabilities:
Commodity derivatives	973			—			—			(973		)	—
Foreign currency forwards	—			2,985			—			—			2,985
Interest rate swaps	—			—			1,482			—			1,482
Total liabilities	973			2,985			1,482			(973		)	4,467
Net assets (liabilities) at fair value	$	3,685		$	(2,985	)	$	(1,482	)	$	—		$	(782	)

	December 31, 2017
	Level 1			Level 2			Level 3			Netting⁽¹⁾			Total
Assets:
Commodity derivatives ⁽²⁾	$	602		$	—		$	—		$	(602	)	$	—
Foreign currency forwards	—			2,564			—			—			$	2,564
Total assets	602			2,564			—			(602		)	2,564
Liabilities:
Commodity derivatives	1,970			—			—			(602		)	1,368
Interest rate swaps	—			—			1,228			—			1,228
Total liabilities	1,970			—			1,228			(602		)	2,596
Net assets (liabilities) at fair value	$	(1,368	)	$	2,564		$	(1,228	)	$	—		$	(32	)



(1)	Relates primarily to exchange traded futures. Gain and loss positions on multiple contracts are settled net on a daily basis with the exchange.
(2)	Commodity derivatives are subject to netting arrangements.

Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Table Text Block]

The following table summarizes changes in the fair value of our net financial liabilities classified as Level 3 in the fair value hierarchy (in thousands):



	Year Ended December 31, 2018		Year Ended December 31, 2017
Net liabilities - beginning balance	$	1,228	$	—
Interest rate swaps acquired through acquisition (Note 5)	—		3,275
Transfers out of Level 3	—		—
Realized/Unrealized (gain) loss included in earnings*	163		(1,124		)
Settlements	91		(923		)
Net liabilities - ending balance	$	1,482	$	1,228

*Gains and losses related to interest rate swaps are recorded in interest expense in the condensed consolidated statements of operations and comprehensive income (loss).

Schedule of Notional Quantities for Commodity Derivative Instruments

The following table sets forth the notional quantities for derivative instruments entered into (in thousands of barrels):



	Year Ended December 31,
	2018	2017	2016
Sales	14,013	12,979	33,694
Purchases	13,417	13,430	33,819

Schedule of Derivatives Not Designated as Hedging Instruments Fair Value on Condensed Consolidated Balance Sheets

We have recorded the fair value of our commodity derivative instruments on our consolidated balance sheets in "other current assets" and "other current liabilities" in the following amounts (in thousands):



December 31, 2018				December 31, 2017
Other Current Assets		Other Current Liabilities		Other Current Assets		Other Current Liabilities
$	3,685	$	—	$	—	$	1,368

Schedule of Realized and Unrealized Gains (Losses) from Commodity Derivatives

Realized and unrealized gains (losses) from our commodity derivatives were recorded to product revenue in the following amounts (in thousands):



	Year Ended December 31,
	2018		2017			2016
Realized and unrealized gain (loss)	$	12,088	$	(2,193	)	$	(4,485	)

Schedule of Foreign Assets and Liabilities

The following table summarizes the assets and liabilities (excluding affiliate balances) at December 31, 2018, of our subsidiaries outside the United States (in thousands):



	Canada
Cash and cash equivalents	$	17,107
Other current assets	78,542
Noncurrent assets	590,714
Total assets	$	686,363

Current liabilities	$	69,798
Noncurrent liabilities	76,192
Total liabilities	145,990
Net assets	$	540,373

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2018

Income Tax Disclosure [Abstract]

Consolidated Income (Loss) From Continuing Operations

Our consolidated income from continuing operations before income taxes was generated in the following jurisdictions (in thousands):



	Year Ended December 31,
	2018			2017			2016
U.S.	$	(53,517	)	$	(64,423	)	$	(766	)
Foreign	52,493			44,885			25,297
Consolidated	$	(1,024	)	$	(19,538	)	$	24,531

Summary of Income Tax Expense (Benefit)

The following table summarizes income tax provision (benefit) from continuing operations by jurisdiction (in thousands):



	Year Ended December 31,
	2018			2017			2016
Current income tax provision:
Foreign	$	14,343		$	7,058		$	2,821
U.S. federal	—			—			—
U.S. state	650			383			—
	14,993			7,441			2,821
Deferred income tax provision (benefit):
Foreign	9,610			5,318			4,071
U.S. federal	(664		)	(15,379		)	5,142
U.S. state	(635		)	232			(766		)
	8,311			(9,829		)	8,447
Provision (benefit) for income taxes	$	23,304		$	(2,388	)	$	11,268

Reconciliation of Income Tax Provision (Benefit)

The following table reconciles income tax provision at the U.S. federal statutory rate to the consolidated provision (benefit) for income taxes (in thousands):



	Year Ended December 31,
	2018				2017			2016
Income from continuing operations before income taxes	$	(1,024	)		$	(19,538	)	$	24,531
U.S. federal statutory rate	21		%		35		%	35		%
Provision at statutory rate	(215		)		(6,838		)	8,586
State income taxes—net of federal benefit	13				401			(498		)
Effect of rates other than statutory	3,042				(3,842		)	(1,966		)
Effect of U.S. taxation on foreign branches	11,023				15,710			8,854
Noncontrolling interest	(508		)		—			(3,908		)
Foreign tax credit and offset to branch deferreds	1,447				45,245			(6,026		)
Effect of U.S. deduction of foreign tax	(3,012		)		(7,514		)	—
Impact of valuation allowance on deferred tax assets	—				(65,327		)	6,026
Foreign withholding taxes	10,187				858			18
Stock-based compensation	1,427				1,351			—
Effect of U.S. federal statutory rate reduction	—			—	17,638			—
Other, net	(100		)		(70		)	182
Provision (benefit) for income taxes	$	23,304			$	(2,388	)	$	11,268

Significant Components of Deferred Tax Assets and Liabilities

Significant components of deferred tax assets and liabilities are as follows at December 31, 2018 and 2017 (in thousands):



	December 31,
	2018				2017



Deferred tax assets:
Net operating loss and other credit carryforwards	$	139,274		$	44,867
Compensation and benefits	5,480			7,156
Inventories	44			322
Intangible assets	—			16,714
Pension plan	813			1,760
Allowance for doubtful accounts	577			956
Deferred revenue	2,493			4,953
Foreign tax credit and offset to branch deferreds	55,272			56,719
Other	19,127			28,201
less: valuation allowance	(45,614		)	(45,682		)
Net deferred tax assets	177,466			115,966
Deferred tax liabilities:
Intangible assets	(12,849		)	(5,074		)
Prepaid expenses	—			(1,447		)
Property, plant and equipment	(189,529		)	(108,646		)
Equity investment in partnerships	(3,572		)	(24,315		)
Other	(2,010		)	(2,402		)
Total deferred tax liabilities	(207,960		)	(141,884		)
Net deferred tax liabilities	$	(30,494	)	$	(25,918	)

Long-Term Debt (Tables)

12 Months Ended

Dec. 31, 2018

Debt Instrument [Line Items]

Summary of Long-Term Debt

We had the following outstanding letters of credit at December 31, 2018 (dollars in thousands):



SemGroup $1.0 billion revolving credit facility	2.75%	$	24,335
Secured bi-lateral⁽¹⁾	1.75%	$	19,053

(1) Secured bi-lateral letters of credit are external to the SemGroup $1.0 billion revolving credit facility and do not reduce availability for borrowing on the credit facility.Our long-term debt consisted of the following (dollars in thousands):



	Interest rate at December 31, 2018	December 31, 2018			December 31, 2017
Senior unsecured notes due 2022	5.625%	400,000			400,000
Senior unsecured notes due 2023	5.625%	350,000			350,000
Senior unsecured notes due 2025	6.375%	325,000			325,000
Senior unsecured notes due 2026	7.250%	300,000			300,000
SemGroup $1.0 billion corporate revolving credit facility⁽¹⁾
Alternate base rate borrowings	7.250%	24,500			—
Eurodollar borrowings	5.156%	95,000			131,000
HFOTCO acquisition final payment		—			565,868
HFOTCO term loan B ⁽²⁾	5.280%	597,000			532,125
HFOTCO tax exempt notes payable due 2050	3.399%	225,000			225,000
HFOTCO $75 million revolving credit facility		—			60,000
Capital leases		—			25
Unamortized premium (discount) and debt issuance costs, net		(31,666		)	(30,398		)
Total long-term debt, net		2,284,834			2,858,620
Less: current portion of long-term debt		6,000			5,525
Noncurrent portion of long-term debt, net		$	2,278,834		$	2,853,095


(1)	SemGroup $1.0 billion corporate revolving credit facility matures on May 15, 2021.


(2)	HFOTCO term loan B is due in quarterly installments of $1.5 million, with a final payment due on June 26, 2025.

Early Redemption Premium Percentages [Table Text Block]



2022 Notes
From and after July 15, 2018		102.813%
From and after July 15, 2019		101.406%
From and after July 15, 2020		100.000%



2023 Notes
Not redeemable before May 15, 2019
From and after May 15, 2019		102.813%
From and after May 15, 2020		101.406%
From and after May 15, 2021		100.000%



2025 Notes
Not redeemable before March 15, 2020
From and after March 15, 2020		103.188%
From and after March 15, 2021		101.594%
From and after March 15, 2022		100.000%



2026 Notes
Not redeemable before March 15, 2021
From and after March 15, 2021		103.625%
From and after March 15, 2022		101.813%
From and after March 15, 2023		100.000%

Scheduled Principal Payments of Debt

The following table summarizes the scheduled principal payments as of December 31, 2018 (in thousands):



	Total
For the year ended:
December 31, 2019	$	6,000
December 31, 2020	6,000
December 31, 2021	125,500
December 31, 2022	406,000
December 31, 2023	356,000
Thereafter	1,417,000
Total	$	2,316,500

- Definition

Tabular disclosure of long-debt instruments or arrangements, including identification, terms, features, collateral requirements and other information necessary to a fair presentation. These are debt arrangements that originally required repayment more than twelve months after issuance or greater than the normal operating cycle of the entity, if longer.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 1A
-URI http://asc.fasb.org/extlink&oid=114775744&loc=d3e28541-108399

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21506-112644

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(e),(f))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=114775744&loc=d3e28551-108399

Reference 6: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21521-112644

Reference 7: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21538-112644

Reference 8: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 470
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=75038535&loc=d3e64711-112823

Reference 9: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=114775985&loc=d3e28878-108400

Reference 10: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21475-112644

+ Details

Employee Benefit Plans (Tables)

12 Months Ended

Dec. 31, 2018

Weighted Average Discount Rate [Line Items]

Projected benefit obligations and plan assets of the pension plans

The table below summarizes the balances of the projected benefit obligation and fair value of the plan assets at December 31, 2018 and 2017 (in thousands):



	December 31,
	2018			2017
Projected benefit obligation	$	50,049		$	53,489
Fair value of plan assets	39,197			43,098
Funded status:	$	(10,852	)	$	(10,391	)

Schedule of Allocation of Plan Assets [Table Text Block]

The following information discloses the fair values of our Pension Plans' assets, by asset category, for the periods indicated (in thousands):



	December 31, 2018								December 31, 2017
	Level 1		Level 2		Level 3		Total		Level 1		Level 2		Level 3		Total
Cash and cash equivalents	$	831	$	—	$	—	$	831	$	538	$	—	$	—	$	538
Mutual funds	15,125		—		—		15,125		16,671		—		—		16,671
Pooled mutual funds	—		23,241		—		23,241		—		25,889		—		25,889
Total	$	15,956	$	23,241	$	—	$	39,197	$	17,209	$	25,889	$	—	$	43,098

Commitments and Contingencies (Tables)

12 Months Ended

Dec. 31, 2018

Long-term Purchase Commitment [Line Items]

Summary of Changes in Asset Retirement Obligations

The following table summarizes the changes in this liability from December 31, 2015 through December 31, 2018 (in thousands):



Balance, December 31, 2015	$	15,946
Accretion	2,292
Payments made	(159		)
Currency translation adjustments	469
Balance, December 31, 2016	18,548
Accretion	2,812
Payments made	(160		)
Currency translation adjustments	1,404
Balance, December 31, 2017	22,604
Accretion	4,070
Payments made	(3,111		)
Currency translation adjustments	(1,820		)
Balance, December 31, 2018	$	21,743

Schedule of Future Minimum Rental Payments for Operating Leases [Table Text Block]

Future minimum payments required under operating leases that have initial or remaining non-cancellable lease terms in excess of one year at December 31, 2018, are as follows (in thousands):



For year ending:
December 31, 2019	$	5,795
December 31, 2020	5,796
December 31, 2021	5,312
December 31, 2022	3,455
December 31, 2023	2,453
Thereafter	40,551
Total future minimum lease payments	$	63,362

Summary of Purchase and Sale Commitments [Table Text Block]

At December 31, 2018, such commitments included the following (in thousands):



	Volume (barrels)	Value
Fixed price purchases	4,626	$	230,562
Fixed price sales	4,920	$	246,755
Floating price purchases	14,638	$	750,711
Floating price sales	17,290	$	830,407

Long-term Purchase Commitment [Table Text Block]

Our U.S. Liquids segment has minimum volume commitments for pipeline transportation of crude oil. At December 31, 2018, the approximate amount of future obligations is as follows (in thousands):



For year ending:
December 31, 2019	$	21,865
December 31, 2020	19,751
December 31, 2021	12,976
December 31, 2022	13,231
December 31, 2023	13,496
Thereafter	6,816
Total expected future payments	$	88,135



For year ending:
December 31, 2019	$	9,783
December 31, 2020	9,063
December 31, 2021	7,337
December 31, 2022	6,905
December 31, 2023	2,854
Thereafter	—
Total expected future payments	$	35,942

Equity (Tables)

12 Months Ended

Dec. 31, 2018

Stockholders' Equity Note [Abstract]

Schedule of common stock reflected on the consolidated balance sheet

The common stock for which the par value is reflected on the consolidated balance sheet at December 31, 2018 is summarized below:



	Class A
Shares accounted for at December 31, 2015	43,823,739
Issuance of common shares in public offering	8,625,000
Shares issued for Merger	13,140,020
Issuance of shares under employee and director compensation programs⁽¹⁾	170,772
Shares issued under employee stock purchase plan	46,836
Shares accounted for at December 31, 2016	65,806,367
Shares issued for HFOTCO acquisition	12,383,900
Issuance of shares under employee and director compensation programs⁽¹⁾	149,961
Shares issued under employee stock purchase plan	39,545
Shares accounted for at December 31, 2017	78,379,773
Issuance of shares under employee and director compensation programs⁽¹⁾	202,545
Shares issued under employee stock purchase plan	53,757
Shares accounted for at December 31, 2018⁽²⁾	78,636,075

Dividends Declared [Table Text Block]

The following table sets forth the quarterly dividends per share declared and paid to shareholders for the periods indicated:



Quarter Ending	Dividend Per Share		Date of Record	Date Paid
March 31, 2016	$	0.45	March 7, 2016	March 17, 2016
June 30, 2016	$	0.45	May 16, 2016	May 26, 2016
September 30, 2016	$	0.45	August 15, 2016	August 25, 2016
December 31, 2016	$	0.45	November 18, 2016	November 28, 2016

March 31, 2017	$	0.45	March 7, 2017	March 17, 2017
June 30, 2017	$	0.45	May 15, 2017	May 26, 2017
September 30, 2017	$	0.45	August 18, 2017	August 28, 2017
December 31, 2107	$	0.45	November 20, 2017	December 1, 2017

March 31, 2018	$	0.4725	March 9, 2018	March 19, 2018
June 30, 2018	$	0.4725	May 16, 2018	May 25, 2018
September 30, 2018	$	0.4725	August 20, 2018	August 29, 2018
December 31, 2018	$	0.4725	November 16, 2018	November 26, 2018

March 31, 2019	$	0.4725	March 4, 2019	March 14, 2019

Schedule of Investments in and Advances to Affiliates, Schedule of Investments [Table Text Block]



	Distribution Per Unit		Distributions Paid
Quarter Ended			SemGroup								Noncontrolling Interest Common Units		Total Distributions
Quarter Ended			General Partner		Incentive Distributions		Common Units		Subordinated Units		Noncontrolling Interest Common Units		Total Distributions
December 31, 2015	$	0.6600	$	604	$	5,333	$	13,665	$	—	$	10,622	$	30,224

March 31, 2016	$	0.6600	$	605	$	5,338	$	13,665	$	—	$	10,643	$	30,251
June 30, 2016	$	0.6600	$	605	$	5,339	$	13,665	$	—	$	10,648	$	30,257

- Definition

Tabular disclosure of an entity's stock, including par or stated value per share, number and dollar amount of share subscriptions, shares authorized, shares issued, shares outstanding, number and dollar amount of shares held in an employee trust, dividend per share, total dividends, share conversion features, par value plus additional paid in capital, the value of treasury stock and other information necessary to a fair presentation, and EPS information. Stock by class includes common, convertible, and preferred stocks which are not redeemable or redeemable solely at the option of the issuer. Includes preferred stock with redemption features that are solely within the control of the issuer and mandatorily redeemable stock if redemption is required to occur only upon liquidation or termination of the reporting entity. If more than one issue is outstanding, state the title of each issue and the corresponding dollar amount; dollar amount of any shares subscribed but unissued and the deduction of subscriptions receivable there from; number of shares authorized, issued, and outstanding.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=65888546&loc=d3e21300-112643

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(28))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21553-112644

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 480
-SubTopic 10
-Section S99
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=65877616&loc=d3e177068-122764

Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21538-112644

Reference 6: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21521-112644

Reference 7: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(29))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 8: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(d))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

Reference 9: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21488-112644

Reference 10: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770

Reference 11: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21506-112644

Reference 12: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(27))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 13: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21484-112644

Reference 14: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21475-112644

+ Details

Accumulated Other Comprehensive Income (Loss) (Tables)

12 Months Ended

Dec. 31, 2018

Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]

Components of accumulated other comprehensive income (loss)

The following table presents changes in the components of accumulated other comprehensive loss (in thousands):



	Currency Translation			Employee Benefit Plans			Total
Balance, December 31, 2015	$	(57,201	)	$	(1,361	)	$	(58,562	)
Currency translation adjustment, net of income tax benefit of $8,672	(14,224		)	—			(14,224		)
Changes related to benefit plans, net of income tax benefit of $417	—			(1,128		)	(1,128		)
Balance, December 31, 2016	(71,425		)	(2,489		)	(73,914		)
Currency translation adjustment, net of income tax expense of $12,404	20,411			—			20,411
Changes related to benefit plans, net of income tax expense of $99	—			(298		)	(298		)
Balance, December 31, 2017	(51,014		)	(2,787		)	(53,801		)
Currency translation adjustment, net of income tax benefit of $4,949	(32,379		)	—			(32,379		)
Currency translation adjustment reclassified to gain on disposal, net of income tax expense of $11,769	37,577			—			37,577
Changes related to benefit plans, net of income tax benefit of $311	—			(2,644		)	(2,644		)
Balance, December 31, 2018	$	(45,816	)	$	(5,431	)	$	(51,247	)

Revenue Revenue (Tables)

12 Months Ended

Dec. 31, 2018

Revenue from Contract with Customer [Abstract]

Disaggregation of Revenue [Table Text Block]

Our revenue is disaggregated by segment and by activity below (in thousands):



	Year Ended December 31,
	2018			2017			2016
U.S. Liquids
Product sales	$	1,680,327		$	1,299,343		$	716,570
Pipeline transportation	84,878			43,642			23,099
Truck transportation	23,553			31,351			41,754
Storage fees	161,498			85,712			27,673
Facility service fees	49,896			27,658			18,283
Lease revenue	17,549			5,843			—

U.S. Gas
Product sales	210,827			180,581			167,319
Service fees	54,494			52,637			51,651

Canada
Service fees	134,059			120,575			75,715
Other revenue	59,075			62,657			57,501

Corporate and Other
Product sales	31,319			153,164			136,448
Storage fees	7,753			22,764			20,542
Service fees	3,070			7,160			6,537
Intersegment eliminations	(15,036		)	(11,170		)	(10,928		)

Total revenue	$	2,503,262		$	2,081,917		$	1,332,164

Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Table Text Block]

However, certain of our agreements, such as "take-or-pay" agreements, do not qualify for the practical expedient. The amount and timing of revenue recognition for such contracts is presented below (in thousands):



	2019		2020		2021		2022		2023		Thereafter
Expected timing of revenue recognized for remaining performance obligations	$	280,984	$	227,981	$	186,465	$	169,252	$	163,193	$	1,349,773

Contract with Customer, Asset and Liability [Table Text Block]

The balance of noncurrent receivables from customer contracts was (in thousands):



	December 31, 2018		December 31, 2017
Noncurrent receivables	$	11,496	$	—

Earnings Per Share (Tables)

12 Months Ended

Dec. 31, 2018

Earnings Per Share [Abstract]

Schedule of Earnings Per Share, Basic, by Common Class, Including Two Class Method [Table Text Block]

The following summarizes the calculation of diluted earnings per share for the years ended December 31, 2018, 2017 and 2016 (in thousands, except per share amounts):



	Year Ended December 31, 2018
	Continuing Operations			Discontinued Operations		Net
Loss	$	(24,328	)	$	—	$	(24,328	)
less: Income attributable to noncontrolling interest	2,421			—		2,421
Loss attributable to SemGroup	$	(26,749	)	$	—	$	(26,749	)
Less: cumulative preferred stock dividends	23,790			—		23,790
Net loss attributable to common shareholders	(50,539		)	—		(50,539		)
Weighted average common stock outstanding	78,313			78,313		78,313
Effect of dilutive securities	—			—		—
Diluted weighted average common stock outstanding	78,313			78,313		78,313
Diluted loss per share	$	(0.65	)	$	—	$	(0.65	)



	Year Ended December 31, 2017
	Continuing Operations			Discontinued Operations		Net
Loss	$	(17,150	)	$	—	$	(17,150	)
less: Income attributable to noncontrolling interest	—			—		—
Loss attributable to SemGroup	$	(17,150	)	$	—	$	(17,150	)
Weighted average common stock outstanding	71,418			71,418		71,418
Effect of dilutive securities	—			—		—
Diluted weighted average common stock outstanding	71,418			71,418		71,418
Diluted loss per share	$	(0.24	)	$	—	$	(0.24	)



	Year Ended December 31, 2016
	Continuing Operations		Discontinued Operations			Net
Income	$	13,263	$	(1	)	$	13,262
less: Income attributable to noncontrolling interest	11,167		—			11,167
Income attributable to SemGroup	$	2,096	$	(1	)	$	2,095
Weighted average common stock outstanding	51,889		51,889			51,889
Effect of dilutive securities	392		392			392
Diluted weighted average common stock outstanding	52,281		52,281			52,281
Diluted earnings per share	$	0.04	$	—		$	0.04

The following summarizes the calculation of basic earnings per share for the years ended December 31, 2018, 2017 and 2016 (in thousands, except per share amounts):



	Year Ended December 31, 2018
	Continuing Operations			Discontinued Operations		Net
Loss	$	(24,328	)	$	—	$	(24,328	)
less: Income attributable to noncontrolling interest	2,421			—		2,421
Loss attributable to SemGroup	$	(26,749	)	$	—	$	(26,749	)
less: cumulative preferred stock dividends	23,790			—		23,790
Net loss attributable to common shareholders	(50,539		)	—		(50,539		)
Weighted average common stock outstanding	78,313			78,313		78,313
Basic loss per share	$	(0.65	)	$	—	$	(0.65	)



	Year Ended December 31, 2017
	Continuing Operations			Discontinued Operations		Net
Loss	$	(17,150	)	$	—	$	(17,150	)
less: Income attributable to noncontrolling interest	—			—		—
Loss attributable to SemGroup	$	(17,150	)	$	—	$	(17,150	)
Weighted average common stock outstanding	71,418			71,418		71,418
Basic loss per share	$	(0.24	)	$	—	$	(0.24	)



	Year Ended December 31, 2016
	Continuing Operations		Discontinued Operations			Net
Income	$	13,263	$	(1	)	$	13,262
less: Income attributable to noncontrolling interest	11,167		—			11,167
Income attributable to SemGroup	$	2,096	$	(1	)	$	2,095
Weighted average common stock outstanding	51,889		51,889			51,889
Basic earnings per share	$	0.04	$	—		$	0.04

Equity-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2018

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Schedule of unvested share activity

The activity related to these awards during the period from December 31, 2015 to December 31, 2018 is summarized below:



	Unvested Shares		Average Grant Date Fair Value		Aggregate Fair Value of Shares (in thousands)
Outstanding at December 31, 2015	411,308		$	75.25
Awards granted - 2016	702,309		$	19.18
Awards vested - 2016	(168,096	)	$	20.38	$	3,426
Awards forfeited - 2016	(34,255	)	$	42.42
Outstanding at December 31, 2016	911,266		$	31.09
Awards granted - 2017	377,766		$	35.22
Awards vested - 2017	(149,961	)	$	33.60	$	5,039
Awards forfeited - 2017	(54,981	)	$	81.80
Outstanding at December 31, 2017	1,084,090		$	29.07
Awards granted - 2018	781,100		$	22.10
Awards vested - 2018	(202,545	)	$	23.18	$	4,695
Awards forfeited - 2018	(188,410	)	$	49.72
Outstanding at December 31, 2018	1,474,235		$	21.04

Schedule of Share-based Payment Award Valuation Assumptions [Table Text Block]

The following table sets forth the assumptions used in the valuations of these awards granted in 2017 and 2016:



	2017	2016
Volatility	54.2%	51.9%
Risk-free interest rate	1.57%	0.98%

Rose Rock Midstream L P [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Schedule of Share-based Compensation, Restricted Stock Units Award Activity [Table Text Block]

The activity related to these awards is summarized below:



	Unvested Units		Average Grant Date Fair Value		Aggregate Fair Value of Units (in thousands)
Outstanding at December 31, 2015	100,191		$	38.70
Awards granted - 2016	117,204		$	9.62
Awards vested - 2016	(57,458	)	$	11.58	$	665
Awards forfeited - 2016	(1,846	)	$	26.55
Awards converted to SemGroup awards	(158,091	)	$	19.57
Outstanding at December 31, 2016	—		$	—

Segments (Tables)

12 Months Ended

Dec. 31, 2018

Segment Reporting Information [Line Items]

Schedule of Segment Reporting Information

Our results by segment are presented in the tables below (in thousands):



	Year Ended December 31,
	2018			2017			2016
Revenues:
U.S. Liquids
External	$	2,017,701		$	1,493,548		$	827,379
U.S. Gas
External	250,285			222,048			208,042
Intersegment	15,036			11,170			10,928
Canada
External	193,134			183,232			133,216
Corporate and Other
External	42,142			183,089			163,527
Intersegment	(15,036		)	(11,170		)	(10,928		)
Total Revenues	$	2,503,262		$	2,081,917		$	1,332,164

	Year Ended December 31,
	2018			2017			2016
Earnings from equity method investments:
U.S. Liquids	$	57,625		$	67,345		$	71,569
Corporate and Other	47			(14		)	2,147
Total earnings from equity method investments	$	57,672		$	67,331		$	73,716

	Year Ended December 31,
	2018			2017			2016
Depreciation and amortization:
U.S. Liquids	$	142,237		$	88,738		$	32,449
U.S. Gas	42,997			37,059			36,170
Canada	21,051			18,530			16,867
Corporate and Other	2,969			14,094			13,318
Total depreciation and amortization	$	209,254		$	158,421		$	98,804



	Year Ended December 31,
	2018			2017			2016
Income tax expense (benefit):
U.S. Liquids	$	575		$	362		$	—
Canada	11,018			8,863			3,667
Corporate and Other	11,711			(11,613		)	7,601
Total income tax expense (benefit)	$	23,304		$	(2,388	)	$	11,268

	Year Ended December 31,
	2018			2017			2016
Segment profit:
U.S. Liquids	$	309,423		$	229,208		$	190,768
U.S. Gas	67,070			67,805			66,530
Canada	81,330			76,274			53,264
Corporate and Other	9,726			33,236			39,534
Total segment profit	$	467,549		$	406,523		$	350,096

	Year Ended December 31,
	2018			2017			2016
Reconciliation of segment profit to net income (loss):
Total segment profit	$	467,549		$	406,523		$	350,096
Less:
Adjustment to reflect equity earnings on an EBITDA basis	19,532			26,890			28,757
Net unrealized loss (gain) related to derivative instruments	(5,053		)	40			989
General and administrative expense	91,568			113,779			84,183
Depreciation and amortization	209,254			158,421			98,804
Loss (gain) on disposal or impairment, net	(3,563		)	13,333			16,048
Interest expense	149,714			103,009			62,650
Loss on early extinguishment of debt	—			19,930			—
Foreign currency transaction loss (gain)	9,501			(4,709		)	4,759
Loss (gain) on sale or impairment of non-operated equity method investment	—			—			30,644
Other expense (income), net	(2,380		)	(4,632		)	(1,269		)
Income tax expense (benefit)	23,304			(2,388		)	11,268
Loss from discontinued operations	—			—			1
Net income (loss)	$	(24,328	)	$	(17,150	)	$	13,262

	Year Ended December 31,
	2018			2017			2016
Additions to long-lived assets, including acquisitions and contributions to equity method investments:
U.S. Liquids	$	119,064		$	2,289,218		$	240,242
U.S. Gas	31,102			100,537			21,913
Canada	218,566			113,263			34,506
Corporate and Other	1,804			18,062			28,020
Total additions to long-lived assets	$	370,536		$	2,521,080		$	324,681



	December 31,
	2018		2017
Total assets (excluding intersegment receivables):
U.S. Liquids	$	3,689,384	$	3,871,334
U.S. Gas	716,837		714,777
Canada	684,418		518,900
Corporate and Other	119,668		271,806
Total	$	5,210,307	$	5,376,817

	December 31,
	2018		2017
Equity investments:
U.S. Liquids	$	255,043	$	266,362
Corporate and Other	18,966		18,919
Total equity investments	$	274,009	$	285,281

Supplemental Cash Flow Information (Tables)

12 Months Ended

Dec. 31, 2018

Supplemental Cash Flow Information [Abstract]

Schedule of Changes in Operating Assets and Liabilities

The following table summarizes the changes in the components of operating assets and liabilities, net of the effects of acquisitions (in thousands):



	Year Ended December 31,
	2018			2017			2016
Decrease (increase) in restricted cash	$	33		$	(1	)	$	(1	)
Decrease (increase) in accounts receivable	78,624			(237,394		)	(90,810		)
Decrease (increase) in receivable from affiliates	685			23,764			(19,541		)
Decrease (increase) in inventories	52,166			(17,862		)	(30,686		)
Decrease (increase) in other current assets	(3,406		)	2,947			634
Decrease (increase) in other assets	(1,636		)	(14,307		)	(297		)
Increase (decrease) in accounts payable and accrued liabilities	(78,829		)	209,982			94,687
Increase (decrease) in payable to affiliates	(3,198		)	(19,537		)	21,475
Increase (decrease) in other noncurrent liabilities	1,374			19,385			2,573
	$	45,813		$	(33,023	)	$	(21,966	)

Quarterly Financial Data (Tables)

12 Months Ended

Dec. 31, 2018

Quarterly Financial Data [Abstract]

Summarized Information on the Consolidated Results of Operations

Summarized information on our consolidated results of operations for the quarters during the year ended December 31, 2018 is shown below (in thousands, except per share amounts):



	First Quarter			Second Quarter				Third Quarter			Fourth Quarter			Total
Total revenues	$	661,609		$	595,794			$	633,996		$	611,863		$	2,503,262
Loss (gain) on disposal or impairment, net	(3,566		)	1,824				(383		)	(1,438		)	(3,563		)
Other operating costs and expenses	642,936			576,975				609,208			579,567			2,408,686
Total expenses	639,370			578,799				608,825			578,129			2,405,123
Earnings from equity method investments	12,614			14,351				14,528			16,179			57,672
Operating income	34,853			31,346				39,699			49,913			155,811
Other expenses, net	44,805			37,685				33,935			40,410			156,835
Income (loss) before income taxes	(9,952		)	(6,339		)		5,764			9,503			(1,024		)
Income tax expense (benefit)	23,083			(3,613		)		(2,697		)	6,531			23,304
Net income (loss)	(33,035		)	(2,726		)		8,461			2,972			(24,328		)
Less: net income attributable to noncontrolling interest	—			—				—			2,421			2,421
Net income (loss) attributable to SemGroup	(33,035		)	(2,726		)	—	8,461			551			(26,749		)
Less: cumulative preferred stock dividends	4,832			6,211				6,317			6,430			23,790
Net income (loss) attributable to common shareholders	$	(37,867	)	$	(8,937	)		$	2,144		$	(5,879	)	$	(50,539	)
Earnings (loss) per share—basic	$	(0.48	)	$	(0.11	)		$	0.03		$	(0.08	)	$	(0.65	)
Earnings (loss) per share—diluted	$	(0.48	)	$	(0.11	)		$	0.03		$	(0.08	)	$	(0.65	)

Summarized information on our consolidated results of operations for the quarters during the year ended December 31, 2017 is shown below (in thousands, except per share amounts):



	First Quarter				Second Quarter				Third Quarter				Fourth Quarter				Total
Total revenues	$	456,100			$	473,089			$	545,922			$	606,806			$	2,081,917
Loss (gain) on disposal or impairment, net	2,410				(234		)		41,625				(30,468		)		13,333
Other operating costs and expenses	447,392				465,874				549,442				579,147				2,041,855
Total expenses	449,802				465,640			—	591,067			—	548,679			—	2,055,188
Earnings from equity method investments	17,091				17,753				17,367				15,120				67,331
Operating income (loss)	23,389				25,202			—	(27,778		)	—	73,247			—	94,060
Other expenses, net	33,571				11,966				28,574				39,487				113,598
Income (loss) from continuing operations before income taxes	(10,182		)	—	13,236			—	(56,352		)	—	33,760			—	(19,538		)
Income tax expense (benefit)	95				3,625				(37,249		)		31,141				(2,388		)
Net income (loss)	$	(10,277	)		$	9,611			$	(19,103	)		$	2,619			$	(17,150	)
Earnings (loss) per share—basic	$	(0.16	)		$	0.15			$	(0.25	)		$	0.03			$	(0.24	)
Earnings (loss) per share—diluted	$	(0.16	)		$	0.15			$	(0.25	)		$	0.03			$	(0.24	)

Related Party Transactions (Tables)

12 Months Ended

Dec. 31, 2018

Related Party Transactions

During the years ended December 31, 2018, 2017 and 2016, we generated the following transactions with related parties (in thousands):



	Year Ended December 31,
	2018		2017		2016
NGL Energy
Revenues	$	18,168	$	45,918	$	61,639
Purchases	$	681	$	29,695	$	57,739

White Cliffs
Crude oil revenues	$	—	$	436	$	4,973
Storage revenues	$	4,350	$	4,350	$	4,350
Transportation fees	$	12,506	$	11,298	$	10,797
Management fees	$	545	$	519	$	494
Crude oil purchases	$	6,201	$	11,870	$	4,758

Condensed Consolidating Guarantor Financial Statements (Tables)

12 Months Ended

Dec. 31, 2018

Condensed Financial Statements, Captions [Line Items]

Condensed Balance Sheet [Table Text Block]

Condensed Consolidating Guarantor Balance Sheets



	December 31, 2018
	Parent		Guarantors		Non-guarantors		Consolidating Adjustments			Consolidated
ASSETS
Current assets:
Cash and cash equivalents	$	40,064	$	—	$	50,742	$	(4,151	)	$	86,655
Accounts receivable	83		461,980		100,151		—			562,214
Receivable from affiliates	120		18		157		—			295
Inventories	—		49,397		—		—			49,397
Other current assets	6,682		6,711		3,871		—			17,264
Total current assets	46,949		518,106		154,921		(4,151		)	715,825
Property, plant and equipment	6,732		992,974		2,457,620		—			3,457,326
Equity method investments	3,267,581		1,553,360		—		(4,546,932		)	274,009
Goodwill	—		—		257,302		—			257,302
Other intangible assets	5		119,583		245,450		—			365,038
Other noncurrent assets, net	41,981		4,788		94,038		—			140,807
Total assets	$	3,363,248	$	3,188,811	$	3,209,331	$	(4,551,083	)	$	5,210,307
LIABILITIES, PREFERRED STOCK AND OWNERS’ EQUITY
Current liabilities:
Accounts payable	$	38	$	444,984	$	49,770	$	—		$	494,792
Payable to affiliates	1		3,714		—		—			3,715
Accrued liabilities	33,239		18,424		63,430		2			115,095
Other current liabilities	5,723		3,409		14,423		—			23,555
Total current liabilities	39,001		470,531		127,623		2			637,157
Long-term debt	1,467,083		6,315		811,751		(6,315		)	2,278,834
Deferred income taxes	4,882		—		50,907		—			55,789
Other noncurrent liabilities	1,792		—		36,756		—			38,548
Commitments and contingencies
Redeemable preferred stock	359,658		—		—		—			359,658
Owners' equity excluding noncontrolling interest in consolidated subsidiary	1,490,832		2,711,965		1,832,805		(4,544,770		)	1,490,832
Noncontrolling interest in consolidated subsidiary	—		—		349,489		—			349,489
Total owners’ equity	1,490,832		2,711,965		2,182,294		(4,544,770		)	1,840,321
Total liabilities, preferred stock and owners’ equity	$	3,363,248	$	3,188,811	$	3,209,331	$	(4,551,083	)	$	5,210,307



	December 31, 2017
	Parent			Guarantors		Non-guarantors		Consolidating Adjustments			Consolidated
ASSETS
Current assets:
Cash and cash equivalents	$	32,457		$	—	$	69,872	$	(8,630	)	$	93,699
Accounts receivable	(9		)	562,967		90,526		—			653,484
Receivable from affiliates	58			1,421		212		—			1,691
Current assets held for sale	—			—		38,063		—			38,063
Inventories	—			101,665		—		—			101,665
Other current assets	6,671			4,493		3,133		—			14,297
Total current assets	39,177			670,546		201,806		(8,630		)	902,899
Property, plant and equipment	8,086			1,002,982		2,304,063		—			3,315,131
Equity method investments	3,085,274			2,110,299		—		(4,910,292		)	285,281
Goodwill	—			—		257,302		—			257,302
Other intangible assets	10			127,783		270,850		—			398,643
Other noncurrent assets, net	45,587			3,097		83,916		—			132,600
Noncurrent assets held for sale	—			—		84,961		—			84,961
Total assets	$	3,178,134		$	3,914,707	$	3,202,898	$	(4,918,922	)	$	5,376,817
LIABILITIES AND OWNERS’ EQUITY
Current liabilities:
Accounts payable	$	646		$	533,651	$	53,601	$	—		$	587,898
Payable to affiliates	10			6,961		—		—			6,971
Accrued liabilities	38,747			26,092		66,570		(2		)	131,407
Current liabilities held for sale	—			—		23,847		—			23,847
Other current liabilities	1,922			5,532		8,984		—			16,438
Total current liabilities	41,325			572,236		153,002		(2		)	766,561
Long-term debt	1,474,491			572,558		829,236		(23,190		)	2,853,095
Deferred income taxes	1,892			—		44,693		—			46,585
Other noncurrent liabilities	2,061			—		36,434		—			38,495
Noncurrent liabilities held for sale	—			—		13,716		—			13,716
Commitments and contingencies
Total owners’ equity	1,658,365			2,769,913		2,125,817		(4,895,730		)	1,658,365
Total liabilities and owners’ equity	$	3,178,134		$	3,914,707	$	3,202,898	$	(4,918,922	)	$	5,376,817

Condensed Income Statement [Table Text Block]

Condensed Consolidating Guarantor Statements of Operations



	Year Ended December 31, 2018
	Parent			Guarantors			Non-guarantors			Consolidating Adjustments			Consolidated
Revenues:
Product	$	—		$	1,876,100		$	31,336		$	—		$	1,907,436
Service	—			140,275			378,489			—			518,764
Lease	—			—			17,549			—			17,549
Other	—			—			59,513			—			59,513
Total revenues	—			2,016,375			486,887			—			2,503,262
Expenses:
Costs of products sold, exclusive of depreciation and amortization shown below	—			1,796,716			26,379			—			1,823,095
Operating	—			110,795			173,974			—			284,769
General and administrative	23,580			24,742			43,246			—			91,568
Depreciation and amortization	2,890			76,788			129,576			—			209,254
Loss (gain) on disposal or impairment, net	133,053			(154,302		)	17,686			—			(3,563		)
Total expenses	159,523			1,854,739			390,861			—			2,405,123
Earnings from equity method investments	219,181			73,010			—			(234,519		)	57,672
Operating income	59,658			234,646			96,026			(234,519		)	155,811
Other expenses (income):
Interest expense	68,389			56,217			25,348			(240		)	149,714
Foreign currency transaction (gain) loss	10,246			147			(892		)	—			9,501
Other income, net	(976		)	(138		)	(1,506		)	240			(2,380		)
Total other expenses, net	77,659			56,226			22,950			—			156,835
Income (loss) from continuing operations before income taxes	(18,001		)	178,420			73,076			(234,519		)	(1,024		)
Income tax expense	8,748			—			14,556			—			23,304
Net income (loss)	(26,749		)	178,420			58,520			(234,519		)	(24,328		)
Less: net income attributable to noncontrolling interest	—			—			2,421			—			2,421
Net income (loss) attributable to SemGroup	(26,749		)	178,420			56,099			(234,519		)	(26,749		)
Less: cumulative preferred stock dividends	23,790			—			—			—			23,790
Net income (loss) attributable to common shareholders	$	(50,539	)	$	178,420		$	56,099		$	(234,519	)	$	(50,539	)
Net income (loss)	$	(26,749	)	$	178,420		$	58,520		$	(234,519	)	$	(24,328	)
Other comprehensive income (loss), net of income taxes	(9,420		)	387			11,587			—			2,554
Comprehensive income (loss)	(36,169		)	178,807			70,107			(234,519		)	(21,774		)
Less: comprehensive income attributable to noncontrolling interest	—			—			2,421			—			2,421
Comprehensive income (loss) attributable to SemGroup	$	(36,169	)	$	178,807		$	67,686		$	(234,519	)	$	(24,195	)



	Year Ended December 31, 2017
	Parent			Guarantors			Non-guarantors			Consolidating Adjustments			Consolidated
Revenues:
Product	$	—		$	1,468,754		$	153,164		$	—		$	1,621,918
Service	—			149,197			242,069			—			391,266
Lease	—			—			5,843			—			5,843
Other	—			—			62,890			—			62,890
Total revenues	—			1,617,951			463,966			—			2,081,917
Expenses:
Costs of products sold, exclusive of depreciation and amortization shown below	—			1,383,868			131,023			—			1,514,891
Operating	—			112,863			141,901			—			254,764
General and administrative	42,422			24,492			46,865			—			113,779
Depreciation and amortization	2,294			70,053			86,074			—			158,421
Loss (gain) on disposal or impairment, net	—			70,681			(57,348		)	—			13,333
Total expenses	44,716			1,661,957			348,515			—			2,055,188
Earnings from equity method investments	68,964			(21,499		)	7,494			12,372			67,331
Operating income (loss)	24,248			(65,505		)	122,945			12,372			94,060
Other expenses (income):
Interest expense	40,053			55,119			8,691			(854		)	103,009
Loss on early extinguishment of debt	19,930			—			—			—			19,930
Foreign currency transaction gain	(2,764		)	—			(1,945		)	—			(4,709		)
Other income, net	(913		)	(33		)	(4,540		)	854			(4,632		)
Total other expenses, net	56,306			55,086			2,206			—			113,598
Income (loss) from continuing operations before income taxes	(32,058		)	(120,591		)	120,739			12,372			(19,538		)
Income tax expense (benefit)	(14,908		)	—			12,520			—			(2,388		)
Income (loss) from continuing operations	(17,150		)	(120,591		)	108,219			12,372			(17,150		)
Net income (loss)	$	(17,150	)	$	(120,591	)	$	108,219		$	12,372		$	(17,150	)
Net income (loss)	$	(17,150	)	$	(120,591	)	$	108,219		$	12,372		$	(17,150	)
Other comprehensive income (loss), net of income taxes	(11,987		)	(573		)	32,673			—			20,113
Comprehensive income (loss)	$	(29,137	)	$	(121,164	)	$	140,892		$	12,372		$	2,963



	Year Ended December 31, 2016
	Parent			Guarantors		Non-guarantors			Consolidating Adjustments			Consolidated
Revenues:
Product	$	—		$	872,961	$	136,448		$	—		$	1,009,409
Service	—			162,460		102,570			—			265,030
Other	—			—		57,725			—			57,725
Total revenues	—			1,035,421		296,743			—			1,332,164
Expenses:
Costs of products sold, exclusive of depreciation and amortization shown below	—			761,971		111,460			—			873,431
Operating	—			115,431		96,668			—			212,099
General and administrative	22,349			31,196		30,638			—			84,183
Depreciation and amortization	1,647			68,669		28,488			—			98,804
Loss (gain) on disposal or impairment, net	—			16,115		(67		)	—			16,048
Total expenses	23,996			993,382		267,187			—			1,284,565
Earnings from equity method investments	56,815			81,366		—			(64,424		)	73,757
Loss on issuance of common units by equity method investee	(41		)	—		—			—			(41		)
Operating income	32,778			123,405		29,556			(64,424		)	121,315
Other expenses (income):
Interest expense (income)	(4,002		)	72,277		(4,819		)	(806		)	62,650
Foreign currency transaction loss	—			—		4,759			—			4,759
Loss on sale or impairment of non-operated equity method investment, net	30,644			—		—			—			30,644
Other expenses (income), net	(339		)	63		(1,799		)	806			(1,269		)
Total other expenses (income), net	26,303			72,340		(1,859		)	—			96,784
Income from continuing operations before income taxes	6,475			51,065		31,415			(64,424		)	24,531
Income tax expense	4,380			—		6,888			—			11,268
Income from continuing operations	2,095			51,065		24,527			(64,424		)	13,263
Loss from discontinued operations, net of income taxes	—			—		(1		)	—			(1		)
Net income	2,095			51,065		24,526			(64,424		)	13,262
Less: net income attributable to noncontrolling interests	—			11,167		—			—			11,167
Net income attributable to SemGroup	$	2,095		$	39,898	$	24,526		$	(64,424	)	$	2,095
Net income	$	2,095		$	51,065	$	24,526		$	(64,424	)	$	13,262
Other comprehensive income (loss), net of income taxes	7,360			1,223		(23,935		)	—			(15,352		)
Comprehensive income (loss)	9,455			52,288		591			(64,424		)	(2,090		)
Less: comprehensive income attributable to noncontrolling interests	—			11,167		—			—			11,167
Comprehensive income (loss) attributable to SemGroup	$	9,455		$	41,121	$	591		$	(64,424	)	$	(13,257	)

Condensed Cash Flow Statement [Table Text Block]

Condensed Consolidating Guarantor Statements of Cash Flows



	Year Ended December 31, 2018
	Parent			Guarantors			Non-guarantors			Consolidating Adjustments			Consolidated
Net cash provided by (used in) operating activities	$	(90,572	)	$	144,902		$	215,374		$	—		$	269,704
Cash flows from investing activities:
Capital expenditures	(1,529		)	(65,798		)	(323,407		)	—			(390,734		)
Proceeds from sale of equity method investment and other long-lived assets	—			664			1,294			—			1,958
Contributions to equity method investments	—			(7,781		)	—			—			(7,781		)
Proceeds from business divestitures	156,499			6,753			(15,465		)	—			147,787
Distributions from equity method investees in excess of equity in earnings	—			19,100			—			—			19,100
Net cash provided by (used in) investing activities	154,970			(47,062		)	(337,578		)	—			(229,670		)
Cash flows from financing activities:
Debt issuance costs	(475		)	—			(4,245		)	—			(4,720		)
Borrowings on credit facilities and issuance of senior unsecured notes	660,000			—			598,500			—			1,258,500
Principal payments on credit facilities and other obligations	(678,865		)	(565,904		)	(595,125		)	—			(1,839,894		)
Equity issuance to noncontrolling interest	350,000			—			—			—			350,000
Distributions to noncontrolling interests	(2,932		)	—			—			—			(2,932		)
Proceeds from preferred stock issuance, net of offering costs	342,299			—			—			—			342,299
Repurchase of common stock for payment of statutory taxes due on equity-based compensation	(705		)	—			—			—			(705		)
Dividends paid	(148,482		)	—			—			—			(148,482		)
Proceeds from issuance of common stock under employee stock purchase plan	930			—			—			—			930
Intercompany borrowings (advances), net	(578,561		)	468,079			106,003			4,479			—
Net cash provided by (used in) financing activities	(56,791		)	(97,825		)	105,133			4,479			(45,004		)
Effect of exchange rate changes on cash and cash equivalents	—			(15		)	(2,059		)	—			(2,074		)
Change in cash and cash equivalents	7,607			—			(19,130		)	4,479			(7,044		)
Cash and cash equivalents at beginning of period	32,457			—			69,872			(8,630		)	93,699
Cash and cash equivalents at end of period	$	40,064		$	—		$	50,742		$	(4,151	)	$	86,655



	Year Ended December 31, 2017
	Parent			Guarantors			Non-guarantors			Consolidating Adjustments			Consolidated
Net cash provided by (used in) operating activities	$	(46,556	)	$	93,107		$	93,925		$	—		$	140,476
Cash flows from investing activities:
Capital expenditures	(4,554		)	(135,999		)	(322,160		)	—			(462,713		)
Proceeds from sale of long-lived assets	—			15,565			299,256			—			314,821
Contributions to equity method investments	—			(2,888		)	(23,556		)	—			(26,444		)
Payments to acquire business, net of cash acquired	—			—			(294,239		)	—			(294,239		)
Distributions from equity method investments in excess of equity in earnings	—			18,261			10,513			—			28,774
Net cash provided by (used in) investing activities	(4,554		)	(105,061		)	(330,186		)	—			(439,801		)
Cash flows from financing activities:
Debt issuance costs	(11,116		)	—			—			—			(11,116		)
Borrowings on credit facilities and issuance of senior unsecured notes	1,470,377			—			55,000			—			1,525,377
Principal payments on debt and other obligations	(1,049,652		)	(26		)	(2,750		)	—			(1,052,428		)
Debt extinguishment costs	(16,293		)	—			—			—			(16,293		)
Repurchase of common stock	(1,473		)	—			—			—			(1,473		)
Dividends paid	(129,925		)	—			—			—			(129,925		)
Proceeds from issuance of common stock under employee stock purchase plan	1,114			—			—			—			1,114
Intercompany borrowings (advances), net	(198,467		)	11,980			190,535			(4,048		)	—
Net cash provided by (used in) financing activities	64,565			11,954			242,785			(4,048		)	315,256
Effect of exchange rate changes on cash and cash equivalents	—			—			3,552			—			3,552
Change in cash and cash equivalents	13,455			—			10,076			(4,048		)	19,483
Cash and cash equivalents at beginning of period	19,002			—			59,796			(4,582		)	74,216
Cash and cash equivalents at end of period	$	32,457		$	—		$	69,872		$	(8,630	)	$	93,699



	Year Ended December 31, 2016
	Parent			Guarantors			Non-guarantors			Consolidating Adjustments			Consolidated
Net cash provided by operating activities	$	84,460		$	79,054		$	65,282		$	(58,822	)	$	169,974
Cash flows from investing activities:
Capital expenditures	(2,928		)	(56,102		)	(253,426		)	—			(312,456		)
Proceeds from sale of long-lived assets	—			53			98			—			151
Contributions to equity method investments	—			(4,188		)	—			—			(4,188		)
Proceeds from sale of common units of equity method investee	60,483			—			—			—			60,483
Distributions from equity method investments in excess of equity in earnings	—			27,726			—			—			27,726
Net cash provided by (used in) investing activities	57,555			(32,511		)	(253,328		)	—			(228,284		)
Cash flows from financing activities:
Debt issuance costs	(7,728		)	—			—			—			(7,728		)
Borrowings on credit facilities and issuance of senior unsecured notes	382,500			—			—			—			382,500
Principal payments on credit facilities and other obligations	(396,859		)	(31		)	—			—			(396,890		)
Distributions to noncontrolling interests	—			(32,133		)	—			—			(32,133		)
Proceeds from issuance of common shares, net of offering costs	223,025			—			—			—			223,025
Repurchase of common stock	(965		)	—			—			—			(965		)
Dividends paid	(92,910		)	—			—			—			(92,910		)
Proceeds from issuance of common stock under employee stock purchase plan	1,010			—			—			—			1,010
Intercompany borrowings (advances), net	(235,645		)	(23,437		)	203,278			55,804			—
Net cash provided by (used in) financing activities	(127,572		)	(55,601		)	203,278			55,804			75,909
Effect of exchange rate changes on cash and cash equivalents	—			—			(1,479		)	—			(1,479		)
Change in cash and cash equivalents	14,443			(9,058		)	13,753			(3,018		)	16,120
Cash and cash equivalents at beginning of period	4,559			9,058			46,043			(1,564		)	58,096
Cash and cash equivalents at end of period	$	19,002		$	—		$	59,796		$	(4,582	)	$	74,216

Overview (Details)	Dec. 31, 2018
Ngl Energy Partners Lp [Member] \| General Partner [Member]
Schedule Of Overview [Line Items]
Equity method investment, ownership percentage	11.78%

Consolidation And Basis Of Presentation (Details Textual) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Consolidation And Basis Of Presentation [Line Items]
Property, plant and equipment	$ 3,457,326	$ 3,315,131
Canada [Member] \| Operating Segments [Member]
Consolidation And Basis Of Presentation [Line Items]
Property, plant and equipment	$ 570,800
White Cliffs Pipeline, LLC [Member]
Consolidation And Basis Of Presentation [Line Items]
Equity method investment, ownership percentage	51.00%
General Partner [Member] \| Ngl Energy Partners Lp [Member]
Consolidation And Basis Of Presentation [Line Items]
Equity method investment, ownership percentage	11.78%

Summary of Significant Accounting Policies (Details 1)	12 Months Ended
Summary of Significant Accounting Policies (Details 1)	Dec. 31, 2018
Pipelines and related facilities [Member] \| Minimum [Member]
Property, Plant and Equipment [Line Items]
Useful life property, plant and equipment (in years)	10 years
Pipelines and related facilities [Member] \| Maximum [Member]
Property, Plant and Equipment [Line Items]
Useful life property, plant and equipment (in years)	31 years
Storage and terminal facilities [Member] \| Minimum [Member]
Property, Plant and Equipment [Line Items]
Useful life property, plant and equipment (in years)	10 years
Storage and terminal facilities [Member] \| Maximum [Member]
Property, Plant and Equipment [Line Items]
Useful life property, plant and equipment (in years)	25 years
Natural gas gathering and processing facilities [Member] \| Minimum [Member]
Property, Plant and Equipment [Line Items]
Useful life property, plant and equipment (in years)	10 years
Natural gas gathering and processing facilities [Member] \| Maximum [Member]
Property, Plant and Equipment [Line Items]
Useful life property, plant and equipment (in years)	31 years
Trucking equipment [Member] \| Minimum [Member]
Property, Plant and Equipment [Line Items]
Useful life property, plant and equipment (in years)	3 years
Trucking equipment [Member] \| Maximum [Member]
Property, Plant and Equipment [Line Items]
Useful life property, plant and equipment (in years)	7 years
Office and other property and equipment [Member] \| Minimum [Member]
Property, Plant and Equipment [Line Items]
Useful life property, plant and equipment (in years)	3 years
Office and other property and equipment [Member] \| Maximum [Member]
Property, Plant and Equipment [Line Items]
Useful life property, plant and equipment (in years)	31 years

Summary of Significant Accounting Policies Summary of Significant Accounting Policies (Details 2) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Accounts Receivable, net	$ 562,214,000				$ 653,484,000				$ 562,214,000	$ 653,484,000
Other Assets, Noncurrent	140,807,000				132,600,000				140,807,000	132,600,000
Other Liabilities, Current	6,495,000				3,395,000				6,495,000	3,395,000
Deferred Tax Liabilities, Net, Noncurrent	55,789,000				46,585,000				55,789,000	46,585,000
Retained Earnings (Accumulated Deficit)	(73,971,000)				(50,706,000)				(73,971,000)	(50,706,000)
Revenues	611,863,000	$ 633,996,000	$ 595,794,000	$ 661,609,000	606,806,000	$ 545,922,000	$ 473,089,000	$ 456,100,000	2,503,262,000	2,081,917,000	$ 1,332,164,000
Costs of products sold, exclusive of depreciation and amortization shown below									1,823,095,000
General and Administrative Expense									91,568,000	113,779,000	84,183,000
Income Tax Expense (Benefit)	6,531,000	(2,697,000)	(3,613,000)	23,083,000	31,141,000	(37,249,000)	3,625,000	95,000	23,304,000	(2,388,000)	11,268,000
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	2,972,000	8,461,000	(2,726,000)	(33,035,000)	$ 2,619,000	$ (19,103,000)	$ 9,611,000	$ (10,277,000)	(24,328,000)	(17,150,000)	13,262,000
Net Income (Loss) Available to Common Stockholders, Basic	$ (5,879,000)	$ 2,144,000	$ (8,937,000)	$ (37,867,000)					$ (50,539,000)	$ (17,150,000)	$ 2,095,000
Earnings Per Share, Basic	$ (0.08)	$ 0.03	$ (0.11)	$ (0.48)	$ 0.03	$ (0.25)	$ 0.15	$ (0.16)	$ (0.65)	$ (0.24)	$ 0.04
Earnings Per Share, Diluted	$ (0.08)	$ 0.03	$ (0.11)	$ (0.48)	$ 0.03	$ (0.25)	$ 0.15	$ (0.16)	$ (0.65)	$ (0.24)	$ 0.04
Accounting Standards Update 2014-09 [Member] \| Calculated under Revenue Guidance in Effect before Topic 606 [Member]
Accounts Receivable, net	$ 562,057,000								$ 562,057,000
Other Assets, Noncurrent	119,911,000								119,911,000
Other Liabilities, Current	6,538,000								6,538,000
Deferred Tax Liabilities, Net, Noncurrent	50,045,000								50,045,000
Retained Earnings (Accumulated Deficit)	(89,324,000)								(89,324,000)
Revenues									2,483,962,000
Costs of products sold, exclusive of depreciation and amortization shown below									1,808,129,000
General and Administrative Expense									91,168,000
Income Tax Expense (Benefit)									23,209,000
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest									(28,167,000)
Net Income (Loss) Available to Common Stockholders, Basic									$ (54,378,000)
Earnings Per Share, Basic									$ (0.70)
Earnings Per Share, Diluted									$ (0.70)
Accounting Standards Update 2014-09 [Member] \| Difference between Revenue Guidance in Effect before and after Topic 606 [Member]
Accounts Receivable, net	157,000								$ 157,000
Other Assets, Noncurrent	20,896,000								20,896,000
Other Liabilities, Current	(43,000)								(43,000)
Deferred Tax Liabilities, Net, Noncurrent	5,744,000								5,744,000
Retained Earnings (Accumulated Deficit)	$ 15,353,000								15,353,000
Revenues									19,300,000
Costs of products sold, exclusive of depreciation and amortization shown below									14,966,000
General and Administrative Expense									400,000
Income Tax Expense (Benefit)									95,000
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest									3,839,000
Net Income (Loss) Available to Common Stockholders, Basic									$ 3,839,000
Earnings Per Share, Basic									$ 0.05
Earnings Per Share, Diluted									$ 0.05

Summary of Significant Accounting Policies (Details Textual) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2019 USD ($)	Dec. 31, 2018 USD ($) Country	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Jan. 01, 2019 USD ($)	Jan. 01, 2018 USD ($)
Summary Of Significant Accounting Policies [Line Items]
Document Period End Date		Dec. 31, 2018
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners		49.00%
Inventory valuation adjustment		$ 5,200	$ 455	$ 0
Number of countries in which segments operate \| Country		4
Canada [Member]
Summary Of Significant Accounting Policies [Line Items]
Percentage mark-up on pass-through of recoverable maintenance costs		10.00%
Minimum [Member] \| Canada [Member]
Summary Of Significant Accounting Policies [Line Items]
Maintenance period		4 years
Maximum [Member] \| Canada [Member]
Summary Of Significant Accounting Policies [Line Items]
Maintenance period		5 years
Accounting Standards Update 2016-02 [Member]
Summary Of Significant Accounting Policies [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets					$ 100,000
Accumulated Deficit [Member] \| Accounting Standards Update 2014-09 [Member]
Summary Of Significant Accounting Policies [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets						$ 11,500
Accumulated Deficit [Member] \| Accounting Standards Update 2016-02 [Member]
Summary Of Significant Accounting Policies [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets					$ 200
Crude Oil [Member] \| U.S. Liquids [Member]
Summary Of Significant Accounting Policies [Line Items]
Inventory valuation adjustment		$ 5,200	500
Sem Mexico [Member]
Summary Of Significant Accounting Policies [Line Items]
Disposal Group, Including Discontinued Operation, Inventory, Current			15,600
General and Administrative Expense [Member] \| Accounting Standards Update 2017-07 [Member]
Summary Of Significant Accounting Policies [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Change on Operating Results			$ 3,200	$ (300)
Subsequent Event [Member] \| Accounting Standards Update 2017-07 [Member]
Summary Of Significant Accounting Policies [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Change on Operating Results	$ 10,900

Disposals of Long-Lived Assets Disposals of Long-Lived Assets (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Statement [Line Items]
Other Asset Impairment Charges										$ 3,727	$ 0
Loss (gain) on disposal or impairment	$ (1,438)	$ (383)	$ 1,824	$ (3,566)	$ (30,468)	$ 41,625	$ (234)	$ 2,410	$ (3,563)	13,333	16,048
Sem Mexico [Member] \| Disposal Group, Held-for-sale, Not Discontinued Operations [Member]
Statement [Line Items]
Impairment of Long-Lived Assets to be Disposed of					13,500					13,511
Sem Logistics [Member] \| Disposal Group, Held-for-sale, Not Discontinued Operations [Member]
Statement [Line Items]
Impairment of Long-Lived Assets to be Disposed of					$ 76,700					76,661
SemGas [Member]
Statement [Line Items]
Other Asset Impairment Charges										30,985
Goodwill, Impairment Loss											$ 13,052
Crude Transportation [Member]
Statement [Line Items]
Goodwill, Impairment Loss										26,628
Impairment of Intangible Assets, Finite-lived										12,087
Glass Mountain Pipeline Llc [Member]
Statement [Line Items]
Equity Method Investment, Realized Gain on Disposal									$ (1,100)	$ (150,266)

Disposals of Long-Lived Assets (Details Textual) - USD ($) $ in Thousands			3 Months Ended	12 Months Ended
	Apr. 12, 2018	Mar. 15, 2018	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Current assets held for sale			$ 38,063	$ 0	$ 38,063
Current liabilities held for sale			23,847	0	23,847
Other Asset Impairment Charges					3,727	$ 0
SemGas [Member]
Other Asset Impairment Charges					30,985
Sem Mexico [Member]
Proceeds from Divestiture of Businesses		$ 70,700
Gain (loss) on disposal				1,600
Income (loss) from disposal, excluding discontinued operations, before tax, excluding gain/loss on disposal				2,300
Sem Logistics [Member]
Proceeds from Divestiture of Businesses	$ 73,100
Gain (loss) on disposal				400
Income (loss) from disposal, excluding discontinued operations, before tax, excluding gain/loss on disposal				$ 5,400
Disposal Group, Held-for-sale, Not Discontinued Operations [Member] \| Sem Mexico [Member]
Impairment of Long-Lived Assets to be Disposed of			13,500		13,511
Disposal Group, Including Discontinued Operation, Foreign Currency Translation Gains (Losses)					(30,900)
Disposal Group, Including Discontinued Operation, Pre Tax Income (Loss)					(8,200)
Disposal Group, Including Discontinued Operation, Property, Plant and Equipment			29,400		29,400
Current assets held for sale			34,900		34,900
Current liabilities held for sale			19,400		19,400
Disposal Group, Held-for-sale, Not Discontinued Operations [Member] \| Sem Logistics [Member]
Impairment of Long-Lived Assets to be Disposed of			76,700		76,661
Disposal Group, Including Discontinued Operation, Foreign Currency Translation Gains (Losses)					(22,800)
Disposal Group, Including Discontinued Operation, Pre Tax Income (Loss)					(73,000)
Disposal Group, Including Discontinued Operation, Property, Plant and Equipment			136,800		136,800
Current assets held for sale			3,100		3,100
Current liabilities held for sale			$ 4,400		$ 4,400

Acquisitions (Details Textual) - USD ($) $ in Thousands, shares in Millions				3 Months Ended								12 Months Ended
	Apr. 17, 2018	Jul. 17, 2017	Sep. 30, 2016	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Business Acquisition [Line Items]
Revenues				$ 611,863	$ 633,996	$ 595,794	$ 661,609	$ 606,806	$ 545,922	$ 473,089	$ 456,100	$ 2,503,262	$ 2,081,917	$ 1,332,164
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest				$ 2,972	$ 8,461	$ (2,726)	$ (33,035)	2,619	$ (19,103)	$ 9,611	$ (10,277)	(24,328)	(17,150)	13,262
Gain on pension curtailment												$ 0	3,008	$ 0
HFOTCO LLC [Member]
Business Acquisition [Line Items]
Payments to acquire businesses		$ 297,800
Business Acquisition, Equity Interest Issued or Issuable, Value Assigned		330,000
Revenues													76,900
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest													(2,400)
Business Acquisition, Transaction Costs		$ 19,200
Gain on pension curtailment													3,000
HFOTCO LLC [Member] \| Common Class A [Member]
Business Acquisition [Line Items]
Business Acquisition, Equity Interest Issued or Issuable, Number of Shares		12.4
Rose Rock Midstream L P [Member]
Business Acquisition [Line Items]
Adjustments to Additional Paid in Capital, Stock Issued, Issuance Costs			$ 5,300
Income Tax Effects Allocated Directly to Equity, Equity Transactions			$ 143,300
Rose Rock Midstream L P [Member] \| Common Class A [Member]
Business Acquisition [Line Items]
Business Acquisition, Equity Interest Issued or Issuable, Number of Shares			13.1
Secured Debt [Member] \| HFOTCO LLC [Member]
Business Acquisition [Line Items]
Business Combination, Consideration Transferred, Liabilities Incurred		$ 766,000
Other Pension, Postretirement and Supplemental Plans [Member] \| HFOTCO LLC [Member]
Business Acquisition [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Liabilities, Other		$ 10,000						$ 7,000					$ 7,000
Second Payment [Member]
Business Acquisition [Line Items]
Extinguishment of Debt, Amount	$ 579,600
Second Payment [Member] \| HFOTCO LLC [Member]
Business Acquisition [Line Items]
Extinguishment of Debt, Amount	$ 579,600

Equity Method Investments (Investment Summary) (Details) - USD ($)

3 Months Ended

12 Months Ended

Dec. 31, 2018

Sep. 30, 2018

Jun. 30, 2018

Mar. 31, 2018

Dec. 31, 2017

Sep. 30, 2017

Jun. 30, 2017

Mar. 31, 2017

Dec. 31, 2018

Dec. 31, 2017

Dec. 31, 2016

Schedule of Equity Method Investments [Line Items]

Equity method investments

$ 274,009,000

$ 285,281,000

$ 274,009,000

$ 285,281,000

Earnings from equity method investments

16,179,000

$ 14,528,000

$ 14,351,000

$ 12,614,000

15,120,000

$ 17,367,000

$ 17,753,000

$ 17,091,000

57,672,000

67,331,000

$ 73,757,000

Loss on issuance of common units by equity method investee

(41,000)

Proceeds from Equity Method Investment, Dividends or Distributions, Return of and Return on Capital

76,725,000

95,522,000

104,168,000

White Cliffs Pipeline, LLC [Member]

Schedule of Equity Method Investments [Line Items]

Equity method investments

255,043,000

266,362,000

255,043,000

266,362,000

Earnings from equity method investments

57,625,000

59,851,000

69,007,000

Proceeds from Equity Method Investment, Dividends or Distributions, Return of and Return on Capital

76,725,000

77,511,000

88,839,000

Ngl Energy Partners Lp [Member]

Schedule of Equity Method Investments [Line Items]

Equity method investments

$ 18,966,000

$ 18,919,000

18,966,000

18,919,000

Earnings from equity method investments

^[1]

47,000

(14,000)

2,188,000

Loss on issuance of common units by equity method investee

(41,000.0)

Proceeds from Equity Method Investment, Dividends or Distributions, Return of and Return on Capital

4,873,000

Glass Mountain Pipeline LLC [Member]

Schedule of Equity Method Investments [Line Items]

Earnings from equity method investments

7,494,000

2,562,000

Proceeds from Equity Method Investment, Dividends or Distributions, Return of and Return on Capital

$ 0

$ 18,011,000

$ 10,456,000

[1]	(1) Excluding a loss on issuance of common units of $41.0 thousand for the year ended December 31, 2016

- Definition

This item represents the entity's proportionate share for the period of the net income (loss) of its investee (such as unconsolidated subsidiaries and joint ventures) to which the equity method of accounting is applied. This item includes income or expense related to stock-based compensation based on the investor's grant of stock to employees of an equity method investee.

+ References + Details

Equity Method Investments (Details Textual) - USD ($)	12 Months Ended
Equity Method Investments (Details Textual) - USD ($)	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Apr. 27, 2016
Investment in Non Consolidated Subsidiaries (Textual) [Abstract]
Loss on issuance of common units by equity method investee	$ 0	$ 0	$ (41,000)
Payments to Acquire Equity Method Investments	7,781,000	26,444,000	4,188,000
Proceeds from Sale of Equity Method Investments	$ 0	0	60,483,000
White Cliffs Pipeline, LLC [Member]
Investment in Non Consolidated Subsidiaries (Textual) [Abstract]
Percentage of ownership interest	51.00%
Payments to Acquire Equity Method Investments	$ 6,500,000	1,400,000	2,200,000
Remaining expected capital contributions year one	27,200,000
Ngl Energy Partners Lp [Member]
Investment in Non Consolidated Subsidiaries (Textual) [Abstract]
Loss on issuance of common units by equity method investee			(41,000.0)
Glass Mountain Pipeline LLC [Member]
Investment in Non Consolidated Subsidiaries (Textual) [Abstract]
Proceeds from Sale of Equity Method Investments		300,000,000
Equity Method Investment, Realized Gain (Loss) on Disposal	$ 1,100,000	$ 150,266,000
General Partner [Member] \| Ngl Energy Partners Lp [Member]
Investment in Non Consolidated Subsidiaries (Textual) [Abstract]
Percentage of ownership interest	11.78%
Limited Partner [Member] \| Ngl Energy Partners Lp [Member]
Investment in Non Consolidated Subsidiaries (Textual) [Abstract]
Loss on issuance of common units by equity method investee			(41,000.0)
Proceeds from Sale of Equity Method Investments			$ 60,500,000
Equity Method Investment Units Sold			4,652,568
Equity Method Investment Units Sold Price Per Share				$ 13.00
Equity Method Investment, Realized Gain (Loss) on Disposal			$ 9,100,000
Equity Method Investment, Other than Temporary Impairment			$ 39,800,000

Other Assets (Details 1) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Prepaid Expense	$ 8,379	$ 8,746
Other Assets, Miscellaneous, Current	8,885	5,551
Other Assets, Current	$ 17,264	$ 14,297

Other Assets (Details 2) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Debt Issuance Costs, Line of Credit Arrangements, Net	$ 6,074	$ 8,774
Direct Financing Lease, Net Investment in Lease	69,222	67,825
Deferred Tax Assets, Net, Noncurrent	25,307	33,792
Other Assets, Miscellaneous, Noncurrent	40,204	22,209
Other Assets, Noncurrent	$ 140,807	$ 132,600

Other Assets Other Assets (Details 3) $ in Thousands	Dec. 31, 2018 USD ($)
Other Assets [Abstract]
Capital Leases, Future Minimum Payments Receivable, Next Twelve Months	$ 13,732
Capital Leases, Future Minimum Payments, Receivable in Two Years	13,031
Capital Leases, Future Minimum Payments, Receivable in Three Years	12,800
Capital Leases, Future Minimum Payments, Receivable in Four Years	12,804
Capital Leases, Future Minimum Payments, Receivable in Five Years	12,808
Capital Leases, Future Minimum Payments, Receivable Thereafter	18,151
Capital Leases, Future Minimum Payments Receivable	$ 83,326

Property, Plant and Equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 4,065,229	$ 3,759,973
Accumulated depreciation	(607,903)	(444,842)
Property, plant and equipment, net	3,457,326	3,315,131
Land [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	308,166	273,168
Pipelines and related facilities [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	1,023,502	926,799
Storage and terminal facilities [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	1,247,115	1,111,001
Natural gas gathering and processing facilities [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	1,055,305	940,130
Linefill [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	27,972	25,747
Trucking equipment [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	45,567	45,162
Office and other property and equipment [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	69,498	63,052
Construction-in-progress [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 288,104	$ 374,914

Property, Plant and Equipment (Details Textual) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 4,065,229	$ 3,759,973
Depreciation	173,100	126,300	$ 87,900
Capitalized interest costs	12,600	18,400	$ 17,000
Use Rights [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 120,200	$ 106,200
Useful life property, plant and equipment (in years)	19 years

Goodwill and Other Intangible Assets (Details 1) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Goodwill [Line Items]
Goodwill, Beginning Balance	$ 34,230	$ 48,032
Currency translation adjustments	206	(750)
Goodwill, Ending Balance	257,302	34,230
U.S. Gas [Member]
Goodwill [Line Items]
Goodwill, Impairment Loss		$ 13,052
U.S. Liquids [Member]
Goodwill [Line Items]
Goodwill, Impairment Loss	26,628
HFOTCO LLC [Member] \| U.S. Liquids [Member]
Goodwill [Line Items]
Goodwill, Acquired During Period	257,302
Disposal Group, Held-for-sale, Not Discontinued Operations [Member] \| Sem Mexico [Member]
Goodwill [Line Items]
Goodwill, Reclassification to Held-for-sale	$ 7,808

Goodwill and Other Intangible Assets (Details 2) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Gross	$ 455,052	$ 455,052
Finite-Lived Intangible Assets, Accumulated Amortization	(90,014)	(56,409)
Finite-lived intangible assets, net	365,038	398,643	$ 150,978	$ 162,223
Customer Relationships [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Gross	424,000	424,000
Finite-Lived Intangible Assets, Accumulated Amortization	(67,917)	(49,717)
Finite-lived intangible assets, net	356,083	374,283
Noncompete Agreements [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Gross	30,000	30,000
Finite-Lived Intangible Assets, Accumulated Amortization	(21,250)	(6,250)
Finite-lived intangible assets, net	8,750	23,750
Trade Names [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Gross	52	52
Finite-Lived Intangible Assets, Accumulated Amortization	(47)	(42)
Finite-lived intangible assets, net	5	10
Customer Contracts [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Gross	1,000	1,000
Finite-Lived Intangible Assets, Accumulated Amortization	(800)	(400)
Finite-lived intangible assets, net	$ 200	$ 600

Goodwill and Other Intangible Assets (Details 3) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Net, beginning balance	$ 398,643	$ 150,978	$ 162,223
Amortization	(33,605)	(30,628)	(10,928)
Currency translation adjustments		95	(317)
Finite-Lived Intangible Assets, Net, ending balance	$ 365,038	398,643	$ 150,978
U.S. Liquids [Member]
Finite-Lived Intangible Assets [Line Items]
Impairment of Intangible Assets, Finite-lived		(12,087)
HFOTCO LLC [Member]
Finite-Lived Intangible Assets [Line Items]
Customer contract intangible asset acquired		291,000
Disposal Group, Held-for-sale, Not Discontinued Operations [Member] \| Sem Mexico [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Reclassification to Held-For-Sale		$ (715)

Goodwill and Other Intangible Assets (Details 4) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Goodwill And Other Intangible Assets [Abstract]
For year ending, December 31, 2019	$ 39,455
For year ending, December 31, 2020	30,000
For year ending, December 31, 2021	30,200
For year ending, December 31, 2022	28,600
For year ending, December 31, 2023	27,100
Thereafter	209,683
Total estimated amortization expense	$ 365,038	$ 398,643	$ 150,978	$ 162,223

Goodwill and Other Intangible Assets (Details Textual) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Goodwill [Line Items]
Goodwill, Amortization Period for Income Taxes	15 years
U.S. Liquids [Member]
Goodwill [Line Items]
Goodwill, Impairment Loss		$ 26,628
Impairment of Intangible Assets, Finite-lived		$ 12,087
U.S. Gas [Member]
Goodwill [Line Items]
Goodwill, Impairment Loss			$ 13,052

Financial Instruments Fair Value of Financial Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Not Designated as Hedging Instrument [Member] \| Interest Rate Swap [Member] \| Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets (Liabilities), at Fair Value, Net	$ (1,482)	$ (1,228)	$ 0
Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset	3,685	2,564
Derivative Liability	4,467	2,596
Derivative Assets (Liabilities), at Fair Value, Net	(782)	(32)
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset, Fair Value, Gross Asset	4,658	602
Derivative Asset, Fair Value, Gross Liability	(973)	(602)
Derivative Liability, Fair Value, Gross Liability	973	1,970
Derivative Liability, Fair Value, Gross Asset	(973)	(602)
Derivative Assets (Liabilities), at Fair Value, Net	3,685	(1,368)
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset, Fair Value, Gross Asset	0	2,564
Derivative Liability, Fair Value, Gross Liability	2,985	0
Derivative Assets (Liabilities), at Fair Value, Net	(2,985)	2,564
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset, Fair Value, Gross Asset	0	0
Derivative Liability, Fair Value, Gross Liability	1,482	1,228
Derivative Assets (Liabilities), at Fair Value, Net	(1,482)	(1,228)
Fair Value, Measurements, Recurring [Member] \| Commodity Contract [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset	3,685	0
Derivative Liability	0	1,368
Fair Value, Measurements, Recurring [Member] \| Interest Rate Swap [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability	1,482	1,228
Fair Value, Measurements, Recurring [Member] \| Foreign Exchange Forward [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset		2,564
Derivative Liability	2,985
Fair Value, Measurements, Recurring [Member] \| Not Designated as Hedging Instrument [Member] \| Commodity Contract [Member] \| Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset, Fair Value, Gross Asset	4,658	602
Derivative Asset, Fair Value, Gross Liability	(973)	(602)
Derivative Liability, Fair Value, Gross Liability	973	1,970
Derivative Liability, Fair Value, Gross Asset	(973)	(602)
Fair Value, Measurements, Recurring [Member] \| Not Designated as Hedging Instrument [Member] \| Interest Rate Swap [Member] \| Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability, Fair Value, Gross Liability	1,482	1,228
Fair Value, Measurements, Recurring [Member] \| Not Designated as Hedging Instrument [Member] \| Foreign Exchange Forward [Member] \| Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset, Fair Value, Gross Asset		$ 2,564
Derivative Liability, Fair Value, Gross Liability	$ 2,985

Financial Instruments and Concentrations of Risk Financial Instruments Transfers In and Out of Level 3 (Details) - Fair Value, Inputs, Level 3 [Member] - Not Designated as Hedging Instrument [Member] - Interest Rate Swap [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Net liabilities - beginning balance	$ 1,228	$ 0
Interest rate swaps acquired through acquisition (Note 5)	0	3,275
Transfers out of Level 3	0	0
Realized/Unrealized (gain) loss included in earnings	163	(1,124)
Settlements	91	(923)
Net liabilities - ending balance	$ 1,482	$ 1,228

Financial Instruments Notional Amounts (Details) - Not Designated as Hedging Instrument [Member] - Commodity Contract [Member] - bbl bbl in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Short [Member]
Derivative, Nonmonetary Notional Amount, Volume	14,013	12,979	33,694
Long [Member]
Derivative, Nonmonetary Notional Amount, Volume	13,417	13,430	33,819

Financial Instruments Fair Value of Commodity Derivative Assets and Liabilities (Details) - Not Designated as Hedging Instrument [Member] - Commodity Contract [Member] - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Other Current Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset	$ 3,685	$ 0
Other Current Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability	$ 0	$ 1,368

Financial Instruments Realized and Unrealized Gains and Losses (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Not Designated as Hedging Instrument [Member] \| Commodity Contract [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Realized and unrealized gains (losses) from commodity derivatives	$ 12,088	$ (2,193)	$ (4,485)

Financial Instruments Foreign Assets and Liabilites (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Concentration of net assets outside of the U.S.
Cash and cash equivalents	$ 86,655	$ 93,699	$ 74,216	$ 58,096
Other current assets	17,264	14,297
Total assets	5,210,307	5,376,817
Current liabilities	637,157	$ 766,561
Subsidiaries [Member] \| CANADA
Concentration of net assets outside of the U.S.
Cash and cash equivalents	17,107
Other current assets	78,542
Noncurrent assets	590,714
Total assets	686,363
Current liabilities	69,798
Noncurrent liabilities	76,192
Total liabilities	145,990
Net assets	$ 540,373

Financial Instruments and Concentrations of Risk (Details Textual) $ in Thousands	12 Months Ended
	Dec. 31, 2018 USD ($) employees	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Margin deposits	$ 100	$ 1,900
Derivative Asset, Fair Value, Amount Offset Against Collateral	$ 3,800	500
Number of Employees, Geographic Area [Member] \| Geographic Concentration Risk [Member]
Number of employees \| employees	880
CANADA \| Number of Employees, Geographic Area [Member] \| Geographic Concentration Risk [Member]
Number of employees	265
CANADA \| Workforce Subject to Collective Bargaining Arrangements [Member] \| Unionized Employees Concentration Risk [Member]
Number of employees	55
Largest Customer [Member] \| Sales Revenue, Net [Member] \| Customer Concentration Risk [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	$ 645,000
Largest Customer [Member] \| Cost of Goods, Total [Member] \| Supplier Concentration Risk [Member]
Cost of Goods and Services Sold	$ 248,700
Largest Customer [Member] \| Accounts Receivable [Member] \| Customer Concentration Risk [Member]
Concentration of risk, percentage	28.00%
Three Largest Producers [Member] \| Processing volumes [Member] \| Product Concentration Risk [Member] \| U.S. Gas [Member]
Concentration of risk, percentage	89.00%
Two Largest Producers [Member] \| Gathering volumes [Member] \| Product Concentration Risk [Member] \| U.S. Gas [Member]
Concentration of risk, percentage	83.00%
Not Designated as Hedging Instrument [Member] \| Interest Rate Swap [Member]
Derivative, Notional Amount	$ 524,300	491,100
Not Designated as Hedging Instrument [Member] \| Foreign Exchange Forward [Member]
Derivative, Notional Amount	56,100	197,700
Realized/Unrealized (gain) loss included in earnings	10,200	(2,800)
Not Designated as Hedging Instrument [Member] \| Fair Value, Inputs, Level 3 [Member] \| Interest Rate Swap [Member]
Derivative Assets (Liabilities), at Fair Value, Net	(1,482)	(1,228)	$ 0
Realized/Unrealized (gain) loss included in earnings	163	(1,124)
Fair Value, Measurements, Recurring [Member]
Derivative Assets (Liabilities), at Fair Value, Net	(782)	(32)
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 3 [Member]
Derivative Assets (Liabilities), at Fair Value, Net	(1,482)	(1,228)
Derivative Liability, Fair Value, Gross Liability	1,482	1,228
Derivative Asset	0	0
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member]
Derivative Assets (Liabilities), at Fair Value, Net	(2,985)	2,564
Derivative Liability, Fair Value, Gross Liability	2,985	0
Derivative Asset	0	2,564
Fair Value, Measurements, Recurring [Member] \| Not Designated as Hedging Instrument [Member] \| Fair Value, Inputs, Level 3 [Member] \| Interest Rate Swap [Member]
Derivative Liability, Fair Value, Gross Liability	1,482	1,228
Fair Value, Measurements, Recurring [Member] \| Not Designated as Hedging Instrument [Member] \| Fair Value, Inputs, Level 2 [Member] \| Foreign Exchange Forward [Member]
Derivative Liability, Fair Value, Gross Liability	$ 2,985
Derivative Asset		$ 2,564

Income Taxes (Details 1) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
Income Taxes (Details 1) - USD ($) $ in Thousands	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
U.S.									$ (53,517)	$ (64,423)	$ (766)
Foreign									52,493	44,885	25,297
Income (loss) from continuing operations before income taxes	$ 9,503	$ 5,764	$ (6,339)	$ (9,952)	$ 33,760	$ (56,352)	$ 13,236	$ (10,182)	$ (1,024)	$ (19,538)	$ 24,531

Income Taxes (Details 2) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
Income Taxes (Details 2) - USD ($) $ in Thousands	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Expense (Benefit), Continuing Operations, by Jurisdiction [Abstract]
Foreign									$ 14,343	$ 7,058	$ 2,821
U.S. federal									0	0	0
U.S. state									650	383	0
Current income tax provision (benefit)									14,993	7,441	2,821
Foreign									9,610	5,318	4,071
U.S. federal									(664)	(15,379)	5,142
U.S. state									(635)	232	(766)
Deferred income tax provision (benefit)									8,311	(9,829)	8,447
Provision (benefit) for income taxes	$ 6,531	$ (2,697)	$ (3,613)	$ 23,083	$ 31,141	$ (37,249)	$ 3,625	$ 95	$ 23,304	$ (2,388)	$ 11,268

Income Taxes (Details 3) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
Income Taxes (Details 3) - USD ($) $ in Thousands	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Income (loss) from continuing operations before income taxes	$ 9,503	$ 5,764	$ (6,339)	$ (9,952)	$ 33,760	$ (56,352)	$ 13,236	$ (10,182)	$ (1,024)	$ (19,538)	$ 24,531
U.S. federal statutory rate									21.00%	35.00%	35.00%
Provision at statutory rate									$ (215)	$ (6,838)	$ 8,586
State income taxes—net of federal benefit									13	401	(498)
Effective Income Tax Rate Reconciliation, Tax Credit, Other, Amount									(3,042)	3,842	1,966
Effect of U.S. taxation on foreign branches									11,023	15,710	8,854
Noncontrolling interest									508	0	3,908
Foreign tax credit and offset to branch deferreds									1,447	45,245	(6,026)
Effective Income Tax Rate Reconciliation, Tax Credit, Foreign, Amount									(3,012)	(7,514)	0
Impact of valuation allowance on deferred tax assets									0	(65,327)	6,026
Foreign withholding taxes									10,187	858	18
Effective Income Tax Rate Reconciliation, Nondeductible Expense, Share-based Compensation Cost, Amount									1,427	1,351	0
Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Amount									0	17,638	0
Other, net									(100)	(70)	182
Provision (benefit) for income taxes	$ 6,531	$ (2,697)	$ (3,613)	$ 23,083	$ 31,141	$ (37,249)	$ 3,625	$ 95	$ 23,304	$ (2,388)	$ 11,268

Income Taxes (Details 4) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Components of Deferred Tax Assets [Abstract]
Net operating loss and other credit carryforwards	$ 139,274	$ 44,867
Compensation and benefits	5,480	7,156
Inventories	44	322
Intangible assets	0	16,714
Pension plan	813	1,760
Allowance for doubtful accounts	577	956
Deferred revenue	2,493	4,953
Foreign tax credit and offset to branch deferreds	55,272	56,719
Other	19,127	28,201
less: valuation allowance	(45,614)	(45,682)
Deferred Tax Assets, Net of Valuation Allowance	177,466	115,966
Components of Deferred Tax Liabilities [Abstract]
Intangible assets	(12,849)	(5,074)
Prepaid expenses	0	(1,447)
Property, plant and equipment	(189,529)	(108,646)
Equity Investment in partnerships	(3,572)	(24,315)
Other	(2,010)	(2,402)
Total deferred tax liabilities	(207,960)	(141,884)
Net deferred tax liabilities	$ (30,494)	$ (25,918)

Income Taxes (Details Textual) $ in Millions	12 Months Ended
Income Taxes (Details Textual) $ in Millions	Dec. 31, 2018 USD ($)
Operating Loss Carryforwards [Line Items]
Change in valuation allowance	$ (0.1)
Domestic Tax Authority [Member]
Operating Loss Carryforwards [Line Items]
Net operating loss	535.6
Deferred Tax Assets, Operating Loss Carryforwards, Not Subject to Expiration	350.4
State and Local Jurisdiction [Member]
Operating Loss Carryforwards [Line Items]
Net operating loss	371.0
Foreign Tax Authority [Member]
Operating Loss Carryforwards [Line Items]
Deferred Tax Assets, Operating Loss Carryforwards, Subject to Expiration	0.8
Forgein income tax credits	44.6
Interest Expense [Member] \| Domestic Tax Authority [Member]
Operating Loss Carryforwards [Line Items]
Deferred Tax Assets, Operating Loss Carryforwards, Not Subject to Expiration	$ 31.8

Long-Term Debt (Details 1) - USD ($) $ in Thousands	Dec. 31, 2018	Jun. 26, 2018	Dec. 31, 2017	Sep. 20, 2017	Mar. 15, 2017
Debt Instrument [Line Items]
Capital leases	$ 0		$ 25
Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net	(31,666)		(30,398)
Total long-term debt	2,284,834		2,858,620
less: current portion of long-term debt	6,000		5,525
Noncurrent portion of long-term debt	$ 2,278,834		2,853,095
Second Payment [Member]
Debt Instrument [Line Items]
Debt instrument, interest rate stated percentage
Long-term Debt, Gross	$ 0		565,868
HFOTCO Credit Facility [Member]
Debt Instrument [Line Items]
Long-term Line of Credit		$ 75,000
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Interest Rate at Period End	2.75%
HFOTCO LLC [Member] \| Term Loan B [Member]
Debt Instrument [Line Items]
Debt instrument, interest rate stated percentage	5.28%
Long-term Debt, Gross	$ 597,000	$ 600,000	532,125
HFOTCO LLC [Member] \| Tax Exempt Notes Payable due 2050 [Member]
Debt Instrument [Line Items]
Debt instrument, interest rate stated percentage	3.399%
Long-term Debt, Gross	$ 225,000		225,000
Senior Notes [Member] \| Senior unsecured notes due 2022 [Member]
Debt Instrument [Line Items]
Debt instrument, interest rate stated percentage	5.625%
Long-term Debt, Gross	$ 400,000		400,000
Senior Notes [Member] \| Senior unsecured notes due 2023 [Member]
Debt Instrument [Line Items]
Debt instrument, interest rate stated percentage	5.625%
Long-term Debt, Gross	$ 350,000		350,000
Senior Notes [Member] \| Senior Unsecured Notes due 2025 [Member]
Debt Instrument [Line Items]
Debt instrument, interest rate stated percentage	6.375%				6.375%
Long-term Debt, Gross	$ 325,000		325,000
Senior Notes [Member] \| Senior unsecured notes due 2026 [Member]
Debt Instrument [Line Items]
Debt instrument, interest rate stated percentage	7.25%			7.25%
Long-term Debt, Gross	$ 300,000		300,000
Line of Credit [Member] \| Revolving Credit Facility [Member] \| HFOTCO Credit Facility [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Interest Rate at Period End
Long-term Line of Credit	$ 0		60,000
Alternate Base Rate [Member] \| Line of Credit [Member] \| Revolving Credit Facility [Member] \| Corporate Credit Facility [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Interest Rate at Period End	7.25%
Long-term Line of Credit	$ 24,500		0
Eurodollar [Member] \| Line of Credit [Member] \| Revolving Credit Facility [Member] \| Corporate Credit Facility [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Interest Rate at Period End	5.156%
Long-term Line of Credit	$ 95,000		$ 131,000

Long-Term Debt (Details 2) - Senior Notes [Member]	12 Months Ended
Long-Term Debt (Details 2) - Senior Notes [Member]	Dec. 31, 2018
Senior unsecured notes due 2022 [Member] \| Debt Instrument, Redemption, Period One [Member]
Debt Instrument, Redemption [Line Items]
Early redemption premium	102.813%
Senior unsecured notes due 2022 [Member] \| Debt Instrument, Redemption, Period Two [Member]
Debt Instrument, Redemption [Line Items]
Early redemption premium	101.406%
Senior unsecured notes due 2022 [Member] \| Debt Instrument, Redemption, Period Three [Member]
Debt Instrument, Redemption [Line Items]
Early redemption premium	100.00%
Senior unsecured notes due 2023 [Member] \| Debt Instrument, Redemption, Period One [Member]
Debt Instrument, Redemption [Line Items]
Early redemption premium	102.813%
Senior unsecured notes due 2023 [Member] \| Debt Instrument, Redemption, Period Two [Member]
Debt Instrument, Redemption [Line Items]
Early redemption premium	101.406%
Senior unsecured notes due 2023 [Member] \| Debt Instrument, Redemption, Period Three [Member]
Debt Instrument, Redemption [Line Items]
Early redemption premium	100.00%
Senior Unsecured Notes due 2025 [Member] \| Debt Instrument, Redemption, Period One [Member]
Debt Instrument, Redemption [Line Items]
Early redemption premium	103.188%
Senior Unsecured Notes due 2025 [Member] \| Debt Instrument, Redemption, Period Two [Member]
Debt Instrument, Redemption [Line Items]
Early redemption premium	101.594%
Senior Unsecured Notes due 2025 [Member] \| Debt Instrument, Redemption, Period Three [Member]
Debt Instrument, Redemption [Line Items]
Early redemption premium	100.00%
Senior unsecured notes due 2026 [Member] \| Debt Instrument, Redemption, Period One [Member]
Debt Instrument, Redemption [Line Items]
Early redemption premium	103.625%
Senior unsecured notes due 2026 [Member] \| Debt Instrument, Redemption, Period Two [Member]
Debt Instrument, Redemption [Line Items]
Early redemption premium	101.813%
Senior unsecured notes due 2026 [Member] \| Debt Instrument, Redemption, Period Three [Member]
Debt Instrument, Redemption [Line Items]
Early redemption premium	100.00%

Long-Term Debt Long-Term Debt (Details 3) $ in Thousands	Dec. 31, 2018 USD ($)
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Interest Rate at Period End	2.75%
Letters of credit outstanding	$ 24,335
Bilateral Letter of Credit [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Interest Rate at Period End	1.75%
Letters of credit outstanding	$ 19,053

Long-Term Debt (Details 4) $ in Thousands	Dec. 31, 2018 USD ($)
Debt Instrument [Line Items]
Scheduled principal payments in the next twelve months	$ 6,000
Scheduled principal payments, year two	6,000
Scheduled principal payments, year three	125,500
Scheduled principal payments, year four	406,000
Scheduled principal payments, year five	356,000
Long-term Debt and Capital Lease Obligations, Maturities, Repayments of Principal after Year Five	1,417,000
Long term debt and capital lease obligations excluding discount and deferred costs	$ 2,316,500

Long-Term Debt (Details Textual) - USD ($) $ in Thousands					12 Months Ended
Long-Term Debt (Details Textual) - USD ($) $ in Thousands	Apr. 17, 2018	Sep. 20, 2017	Mar. 17, 2017	Mar. 15, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Jun. 26, 2018
Long Term Debt (Textual) [Abstract]
Gain (Loss) on Extinguishment of Debt					$ 0	$ (19,930)	$ 0
Redemption Premium						15,900
Write off of Deferred Debt Issuance Cost						3,600
Senior Notes [Member]
Long Term Debt (Textual) [Abstract]
Debt Instrument Redemption Price Percentage of Principal					35.00%
Debt Instrument Redemption Price, Prior to Redemption Dates, Premium, Percentage					1.00%
Early redemption premium					101.00%
Revolving Credit Facility [Member]
Long Term Debt (Textual) [Abstract]
Maximum borrowing capacity					$ 1,000,000
Letters of credit outstanding					$ 24,335
Second Payment [Member]
Long Term Debt (Textual) [Abstract]
Debt instrument, interest rate stated percentage
Long-term Debt, Gross					$ 0	565,868
Senior Unsecured Notes due 2021 [Member] \| Senior Notes [Member]
Long Term Debt (Textual) [Abstract]
Debt instrument, interest rate stated percentage				7.50%
Debt Instrument, Face Amount				$ 300,000
HFOTCO Credit Facility [Member]
Long Term Debt (Textual) [Abstract]
Long-term Line of Credit								$ 75,000
HFOTCO Credit Facility [Member] \| Revolving Credit Facility [Member] \| Line of Credit [Member]
Long Term Debt (Textual) [Abstract]
Long-term Line of Credit					$ 0	60,000
Senior Unsecured Notes due 2025 [Member] \| Senior Notes [Member]
Long Term Debt (Textual) [Abstract]
Debt instrument, interest rate stated percentage				6.375%	6.375%
Debt Instrument, Face Amount				$ 325,000
Debt Instrument, Discount, Percentage				98.467%
Debt Instrument, Unamortized Discount				$ 5,000
Proceeds from Issuance of Debt				315,100
Debt Issuance Costs, Gross				4,900
Long-term Debt, Gross					$ 325,000	325,000
Senior unsecured notes due 2026 [Member] \| Senior Notes [Member]
Long Term Debt (Textual) [Abstract]
Debt instrument, interest rate stated percentage		7.25%			7.25%
Debt Instrument, Face Amount		$ 300,000
Debt Instrument, Discount, Percentage		98.453%
Debt Instrument, Unamortized Discount		$ 4,600
Proceeds from Issuance of Debt		290,300
Debt Issuance Costs, Gross		$ 5,100
Long-term Debt, Gross					$ 300,000	300,000
Fair Value, Inputs, Level 3 [Member]
Long Term Debt (Textual) [Abstract]
Long-term Debt, Fair Value					$ 2,200,000
Second Payment [Member]
Long Term Debt (Textual) [Abstract]
Extinguishment of Debt, Amount	$ 579,600
Tender Offer [Member] \| Senior Unsecured Notes due 2021 [Member]
Long Term Debt (Textual) [Abstract]
Extinguishment of Debt, Amount				$ 290,000
Notes called [Member] \| Senior Unsecured Notes due 2021 [Member]
Long Term Debt (Textual) [Abstract]
Extinguishment of Debt, Amount			$ 10,000
US Treasury Rate [Member]
Long Term Debt (Textual) [Abstract]
Debt Instrument Redemption Price, Prior to Redemption Dates, Basis Spread on Variable Discount Rate					5000.00%
HFOTCO LLC [Member] \| Term Loan B [Member]
Long Term Debt (Textual) [Abstract]
Debt instrument, interest rate stated percentage					5.28%
Debt Instrument, Periodic Payment, Principal					$ 1,500
Debt Instrument, Unamortized Discount								1,500
Long-term Debt, Gross					597,000	532,125		$ 600,000
Limit on potential increase in facility					$ 120,000
HFOTCO LLC [Member] \| Tax Exempt Notes Payable due 2050 [Member]
Long Term Debt (Textual) [Abstract]
Debt instrument, interest rate stated percentage					3.399%
Long-term Debt, Gross					$ 225,000	$ 225,000
HFOTCO LLC [Member] \| Eurodollar [Member] \| Term Loan B [Member]
Long Term Debt (Textual) [Abstract]
Debt Instrument, Basis Spread on Variable Rate					2.75%
HFOTCO LLC [Member] \| Alternate Base Rate [Member] \| Term Loan B [Member]
Long Term Debt (Textual) [Abstract]
Debt Instrument, Basis Spread on Variable Rate					1.75%
HFOTCO LLC [Member] \| Maximum Super Senior Leverage Ratio [Member] \| Tax Exempt Notes Payable due 2050 [Member]
Long Term Debt (Textual) [Abstract]
Line of Credit Facility, Covenant Terms					3.50
HFOTCO LLC [Member] \| Minimum interest coverage ratio [Member] \| Tax Exempt Notes Payable due 2050 [Member]
Long Term Debt (Textual) [Abstract]
Line of Credit Facility, Covenant Terms					2.00

Employee Benefit Plans (Details) - Pension Plan [Member] - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation	$ 50,049	$ 53,489
Fair value of plan assets	39,197	43,098
Funded status:	$ (10,852)	$ (10,391)

Employee Benefit Plans (Details Textual) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Postretirement Benefits [Line Items]
Contributions to the defined contribution plans	$ 3,000	$ 3,000	$ 2,700
Other, net of income taxes	(2,644)	(298)	(1,128)
Pension Plan [Member]
Postretirement Benefits [Line Items]
Other, net of income taxes	2,600	300	$ 1,100
Projected benefit obligation	50,049	53,489
Postretirement Health Coverage [Member]
Postretirement Benefits [Line Items]
Projected benefit obligation	1,500	1,700
Canada [Member] \| Pension Plan [Member]
Postretirement Benefits [Line Items]
Funded status of the Pension Plans	2,000	2,300
U.S. Liquids [Member] \| Pension Plan [Member]
Postretirement Benefits [Line Items]
Funded status of the Pension Plans	$ 8,800	$ 8,100

Commitments and Contingencies (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Beginning Balance	$ 22,604	$ 18,548	$ 15,946
Accretion	4,070	2,812	2,292
Payments made	(3,111)	(160)	(159)
Currency translation adjustments	(1,820)	1,404	469
Ending Balance	$ 21,743	$ 22,604	$ 18,548

Commitments and Contingencies (Details 1) $ in Thousands	Dec. 31, 2018 USD ($)
Commitments and Contingencies Disclosure [Abstract]
Operating Leases, Due next twelve months	$ 5,795
Operating Leases, Due in Two Years	5,796
Operating Leases, Due in Three Years	5,312
Operating Leases, Due in Four Years	3,455
Operating Leases, Due in Five Years	2,453
Operating Leases, Thereafter	40,551
Operating Leases, Total future minimum lease payments	$ 63,362

Commitments and Contingencies (Details 2) bbl in Thousands, $ in Thousands	Dec. 31, 2018 USD ($) bbl
Fixed Price Sales [Member]
Summary Of Purchase And Sale Commitments
Sale commitments, Volume (barrels) \| bbl	4,920
Sale commitments, Value \| $	$ 246,755
Floating Price Sales [Member]
Summary Of Purchase And Sale Commitments
Sale commitments, Volume (barrels) \| bbl	17,290
Sale commitments, Value \| $	$ 830,407
Fixed Price Purchases [Member]
Summary Of Purchase And Sale Commitments
Purchase commitments, Volume (barrels) \| bbl	4,626
Purchase commitments, Value \| $	$ 230,562
Floating Price Purchases [Member]
Summary Of Purchase And Sale Commitments
Purchase commitments, Volume (barrels) \| bbl	14,638
Purchase commitments, Value \| $	$ 750,711

Commitments and Contingencies (Details 3) - U.S. Gas [Member] - Fractionation capacity [Member] $ in Thousands	Dec. 31, 2018 USD ($)
Long-term Purchase Commitment [Line Items]
Purchase Obligation, Due in Next Twelve Months	$ 9,783
Purchase Obligation, Due in Second Year	9,063
Purchase Obligation, Due in Third Year	7,337
Purchase Obligation, Due in Fourth Year	6,905
Purchase Obligation, Due in Fifth Year	2,854
Purchase Obligation, Due after Fifth Year	0
Purchase Obligation	$ 35,942

Commitments and Contingencies Commitments and Contingencies (Details 4) - Pipeline transportation capacity [Member] - U.S. Liquids [Member] $ in Thousands	Dec. 31, 2018 USD ($)
Long-term Purchase Commitment [Line Items]
Purchase Obligation, Due in Next Twelve Months	$ 21,865
Purchase Obligation, Due in Second Year	19,751
Purchase Obligation, Due in Third Year	12,976
Purchase Obligation, Due in Fourth Year	13,231
Purchase Obligation, Due in Fifth Year	13,496
Purchase Obligation, Due after Fifth Year	6,816
Purchase Obligation	$ 88,135

Commitments and Contingencies (Details Textual) $ in Millions	12 Months Ended
	Dec. 31, 2018 USD ($) Number_Of_Sites	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Commitments and Contingencies (Textual) [Abstract]
Estimated cost to retire facilities \| $	$ 127.1
Asset Retirement Obligation Additional Estimated Costs Attributable To Third Party Owners Undiscounted \| $	18.1
Operating leases, rent expense \| $	$ 15.1	$ 15.4	$ 15.0
Minimum [Member]
Commitments and Contingencies (Textual) [Abstract]
Notice required to cancel purchase agreements, days	30 days
Maximum [Member]
Commitments and Contingencies (Textual) [Abstract]
Notice required to cancel purchase agreements, days	120 days
Capital Addition Purchase Commitments [Member]
Commitments and Contingencies (Textual) [Abstract]
Purchase Obligation, Due in Next Twelve Months \| $	$ 104.4
Kansas sites [Member]
Commitments and Contingencies (Textual) [Abstract]
Site contingency number of sites checked	6
Sites completing assessment	4
Number of Sites With Limited Soil and Groundwater Impact	2
Number of Sites Requiring Additional Investigation	2
Kansas sites [Member] \| U.S. Liquids [Member]
Commitments and Contingencies (Textual) [Abstract]
Site contingency number of sites checked	5
Kansas sites [Member] \| U.S. Gas [Member]
Commitments and Contingencies (Textual) [Abstract]
Site contingency number of sites checked	1

Redeemable Preferred Stock (Details) - USD ($)							12 Months Ended
Redeemable Preferred Stock (Details) - USD ($)	Mar. 01, 2019	Nov. 26, 2018	Aug. 29, 2018	May 25, 2018	Jan. 19, 2018	Jun. 22, 2016	Dec. 31, 2016	Dec. 31, 2018	Dec. 31, 2017
Preferred Stock, Shares Issued					350,000			350,000	0
Preferred Stock, Par or Stated Value Per Share					$ 0.01			$ 0.01	$ 0.01
Common Stock, Par or Stated Value Per Share					$ 0.01			$ 0.01	$ 0.01
Issuance of common stock						$ 228,500,000	$ 228,546,000
Payments of Stock Issuance Costs						$ 4,300,000
Preferred Stock, Dividend Rate, Percentage					7.00%
Preferred stock per share annualized dividend					$ 70.00
Preferred Stock, Redemption Price Per Share					$ 33.00
Preferred Stock, Minimum Conversion Amount					$ 50,000,000
Minimum required closing share price for the Company to cause conversion					$ 47.85
Minimum cash consideration in change of control to require conversion					90.00%
Option change in control redemption premium, less than 90% cash transaction					101.00%
Maximum parity stock issuable, amount					$ 250,000,000
Maximum aggregate value of outstanding preferred stock to issue parity stock					$ 100,000,000
Preferred stock ownership required for preemptive rights					75.00%
Preferred stock ownership required to have board observer					50.00%
Minimum ownership required to maintain registration rights					5.00%
Dividends, Preferred Stock, Paid-in-kind		$ 6,300,000	$ 6,200,000	$ 4,800,000
Convertible Preferred Stock, Shares Issued upon Conversion								11,132,121
Cumulative Preferred Stock [Member]
Shares Issued, Price Per Share					$ 1,000
Issuance of common stock					$ 350,000,000
Payments of Stock Issuance Costs					$ 7,700,000
On or prior to the first anniversary of the Issue Date [Domain]
Cash Change of Control Conversion Premium					130.00%
On or prior to the second anniversary of the Issue Date [Domain]
Cash Change of Control Conversion Premium					120.00%
On or prior to the third anniversary of the Issue Date [Domain]
Cash Change of Control Conversion Premium					105.00%
After the third anniversary of the Issue Date [Domain]
Cash Change of Control Conversion Premium					101.00%
Subsequent Event [Member]
Dividends, Preferred Stock, Paid-in-kind	$ 6,400,000

Equity (Details 1) - Common Class A [Member] - shares

12 Months Ended

Jun. 22, 2016

Dec. 31, 2018

Dec. 31, 2017

Dec. 31, 2016

Schedule of Common Stock

Common Stock, Shares, Outstanding

78,379,773

^[1]

65,806,367

43,823,739

Stock Issued During Period, Shares, Restricted Stock Award, Net of Forfeitures

^[2]

202,545

149,961

170,772

Stock Issued During Period, Shares, Employee Stock Purchase Plans

53,757

39,545

46,836

Stock Issued During Period, Shares, New Issues

8,625,000

Stock Issued During Period, Shares, Acquisitions

12,383,900

13,140,020

Common Stock, Shares, Outstanding

78,636,075

^[1]

78,379,773

^[1]

65,806,367

[1]

[2]

Equity Equity (Details 2) - $ / shares	Mar. 14, 2019	Nov. 26, 2018	Aug. 29, 2018	May 25, 2018	Mar. 19, 2018	Dec. 01, 2017	Aug. 28, 2017	May 26, 2017	Mar. 17, 2017	Nov. 28, 2016	Aug. 25, 2016	May 26, 2016	Mar. 17, 2016
Dividends paid		$ 0.4725	$ 0.4725	$ 0.4725	$ 0.4725	$ 0.45	$ 0.45	$ 0.45	$ 0.45	$ 0.45	$ 0.45	$ 0.45	$ 0.45
Subsequent Event [Member]
Common Stock, Dividends, Per Share, Declared	$ 0.4725

Equity Equity (Details 3) - Rose Rock Midstream L P [Member] - USD ($) $ / shares in Units, $ in Thousands	Aug. 12, 2016	May 13, 2016	Feb. 12, 2016
Distribution of Q4 2015 Earnings [Member]
Distribution Made to Limited Partner, Distributions Paid, Per Unit			$ 0.6600
Partners' Capital Account, Distributions			$ 30,224
Distribution of Q1 2016 Earnings [Member]
Distribution Made to Limited Partner, Distributions Paid, Per Unit		$ 0.6600
Partners' Capital Account, Distributions		$ 30,251
Distribution of Q2 2016 Earnings [Member]
Distribution Made to Limited Partner, Distributions Paid, Per Unit	$ 0.6600
Partners' Capital Account, Distributions	$ 30,257
Parent [Member] \| General Partner [Member] \| Distribution of Q4 2015 Earnings [Member]
General Partners' Capital Account, Period Distribution Amount			604
Incentive Distribution, Distribution			5,333
Parent [Member] \| General Partner [Member] \| Distribution of Q1 2016 Earnings [Member]
General Partners' Capital Account, Period Distribution Amount		605
Incentive Distribution, Distribution		5,338
Parent [Member] \| General Partner [Member] \| Distribution of Q2 2016 Earnings [Member]
General Partners' Capital Account, Period Distribution Amount	605
Incentive Distribution, Distribution	5,339
Common Units [Member] \| Parent [Member] \| Limited Partner [Member] \| Distribution of Q4 2015 Earnings [Member]
Limited Partners' Capital Account, Distribution Amount			13,665
Common Units [Member] \| Parent [Member] \| Limited Partner [Member] \| Distribution of Q1 2016 Earnings [Member]
Limited Partners' Capital Account, Distribution Amount		13,665
Common Units [Member] \| Parent [Member] \| Limited Partner [Member] \| Distribution of Q2 2016 Earnings [Member]
Limited Partners' Capital Account, Distribution Amount	13,665
Common Units [Member] \| Noncontrolling Interest [Member] \| Limited Partner [Member] \| Distribution of Q4 2015 Earnings [Member]
Limited Partners' Capital Account, Distribution Amount			10,622
Common Units [Member] \| Noncontrolling Interest [Member] \| Limited Partner [Member] \| Distribution of Q1 2016 Earnings [Member]
Limited Partners' Capital Account, Distribution Amount		10,643
Common Units [Member] \| Noncontrolling Interest [Member] \| Limited Partner [Member] \| Distribution of Q2 2016 Earnings [Member]
Limited Partners' Capital Account, Distribution Amount	10,648
Subordinated Units [Member] \| Parent [Member] \| Limited Partner [Member] \| Distribution of Q4 2015 Earnings [Member]
Limited Partners' Capital Account, Distribution Amount			$ 0
Subordinated Units [Member] \| Parent [Member] \| Limited Partner [Member] \| Distribution of Q1 2016 Earnings [Member]
Limited Partners' Capital Account, Distribution Amount		$ 0
Subordinated Units [Member] \| Parent [Member] \| Limited Partner [Member] \| Distribution of Q2 2016 Earnings [Member]
Limited Partners' Capital Account, Distribution Amount	$ 0

Equity (Details Textual) - USD ($) $ / shares in Units, $ in Thousands					12 Months Ended
	Oct. 22, 2018	Jul. 17, 2017	Sep. 30, 2016	Jun. 22, 2016	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Jan. 19, 2018
Equity [Line Items]
Common Stock, Par or Stated Value Per Share					$ 0.01	$ 0.01		$ 0.01
Common stock shares authorized					190,000,000	100,000,000
Preferred Stock, Shares Authorized					4,000,000	4,000,000
Preferred Stock, Shares Issued					350,000	0		350,000
Issuance of common stock				$ 228,500			$ 228,546
Payments of Stock Issuance Costs				$ 4,300
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners					49.00%
Proceeds from Issuance of Preferred Stock and Preference Stock					$ 342,299	$ 0	$ 0
Common Class A [Member]
Equity [Line Items]
Shares Paid for Tax Withholding for Share Based Compensation					57,041	42,347	46,941
Common Stock, Par or Stated Value Per Share					$ 0.01
Common stock shares authorized					180,000,000
Stock Issued During Period, Shares, New Issues				8,625,000			8,625,000
Shares Issued, Price Per Share				$ 27.00
Stock Issued During Period, Shares, Acquisitions						12,383,900	13,140,020
Class B [Member]
Equity [Line Items]
Common stock shares authorized					10,000,000
Rose Rock Midstream L P [Member]
Equity [Line Items]
Adjustments to Additional Paid in Capital, Stock Issued, Issuance Costs			$ 5,300
Income Tax Effects Allocated Directly to Equity, Equity Transactions			$ (143,300)
Rose Rock Midstream L P [Member] \| Common Class A [Member]
Equity [Line Items]
Stock Issued During Period, Shares, Acquisitions			13,100,000
HFOTCO LLC [Member]
Equity [Line Items]
Business Acquisition, Equity Interest Issued or Issuable, Value Assigned		$ 330,000
Business Acquisition, Share Price		$ 26.68
HFOTCO LLC [Member] \| Common Class A [Member]
Equity [Line Items]
Stock Issued During Period, Shares, Acquisitions		12,400,000
Maurepas Pipeline LLC [Member]
Equity [Line Items]
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners	49.00%				49.00%
Noncontrolling Interest [Member]
Equity [Line Items]
Proceeds from Issuance of Preferred Stock and Preference Stock	$ 350,000
Dividends, Preferred Stock, Cash	2,200
Base price, repurchase option on noncontrolling interest	$ 350,000
Annual increase is base price, repurchase option, noncontrolling interest	1.00%
Preferred stock non-call period	24 months

Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Other Comprehensive Income (Loss), Foreign Currency Translation, Gain (Loss), Reclassification Adjustment from AOCI, after Tax	$ (11,769)
Accumulated Other Comprehensive Income (Loss), Net of Tax	(51,247)	$ (53,801)	$ (73,914)	$ (58,562)
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Gain (Loss) Arising During Period, Net of Tax	(32,379)
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax	5,198	20,411	(14,224)
Other, net of income taxes	(2,644)	(298)	(1,128)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	37,577
Currency Translation [Member]
Other Comprehensive Income (Loss), Tax, Portion Attributable to Parent	4,949	12,404	(8,672)
Accumulated Other Comprehensive Income (Loss), Net of Tax	(45,816)	(51,014)	(71,425)	(57,201)
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Gain (Loss) Arising During Period, Net of Tax	(32,379)
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax		20,411	(14,224)
Other, net of income taxes	0	0	0
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	37,577
Employee Benefit Plans [Member]
Other Comprehensive Income (Loss), Tax, Portion Attributable to Parent	311	99	(417)
Accumulated Other Comprehensive Income (Loss), Net of Tax	(5,431)	(2,787)	(2,489)	$ (1,361)
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Gain (Loss) Arising During Period, Net of Tax	0
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax		0	0
Other, net of income taxes	(2,644)	$ (298)	$ (1,128)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	$ 0

Revenue Revenue (Details 1) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
Revenue Revenue (Details 1) - USD ($) $ in Thousands	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Direct Financing Lease, Revenue									$ 17,549	$ 5,843	$ 0
Revenues	$ 611,863	$ 633,996	$ 595,794	$ 661,609	$ 606,806	$ 545,922	$ 473,089	$ 456,100	2,503,262	2,081,917	1,332,164
Product [Member]
Revenue from Contract with Customer, Excluding Assessed Tax									1,907,436	1,621,918	1,009,409
Other revenue [Member]
Revenue from Contract with Customer, Excluding Assessed Tax									59,513	62,890	57,725
U.S. Liquids [Member]
Direct Financing Lease, Revenue									17,549	5,843	0
Revenues									2,017,701	1,493,548	827,379
U.S. Liquids [Member] \| Product [Member]
Revenue from Contract with Customer, Excluding Assessed Tax									1,680,327	1,299,343	716,570
U.S. Liquids [Member] \| Pipeline transportation [Member]
Revenue from Contract with Customer, Excluding Assessed Tax									84,878	43,642	23,099
U.S. Liquids [Member] \| Truck Transportation Revenue [Member]
Revenue from Contract with Customer, Excluding Assessed Tax									23,553	31,351	41,754
U.S. Liquids [Member] \| Facility Service Fees [Member]
Revenue from Contract with Customer, Excluding Assessed Tax									49,896	27,658	18,283
U.S. Liquids [Member] \| Storage Services [Member]
Revenue from Contract with Customer, Excluding Assessed Tax									161,498	85,712	27,673
SemGas [Member]
Revenues									250,285	222,048	208,042
SemGas [Member] \| Product [Member]
Revenue from Contract with Customer, Excluding Assessed Tax									210,827	180,581	167,319
SemGas [Member] \| Service Fees [Member]
Revenue from Contract with Customer, Excluding Assessed Tax									54,494	52,637	51,651
Canada [Member]
Revenues									193,134	183,232	133,216
Canada [Member] \| Service Fees [Member]
Revenue from Contract with Customer, Excluding Assessed Tax									134,059	120,575	75,715
Canada [Member] \| Other revenue [Member]
Revenue from Contract with Customer, Excluding Assessed Tax									59,075	62,657	57,501
Corporate, Non-Segment [Member]
Revenues									42,142	183,089	163,527
Corporate, Non-Segment [Member] \| Product [Member]
Revenue from Contract with Customer, Excluding Assessed Tax									31,319	153,164	136,448
Corporate, Non-Segment [Member] \| Service Fees [Member]
Revenue from Contract with Customer, Excluding Assessed Tax									3,070	7,160	6,537
Corporate, Non-Segment [Member] \| Storage Services [Member]
Revenue from Contract with Customer, Excluding Assessed Tax									7,753	22,764	20,542
Intersegment Eliminations [Member]
Revenue from Contract with Customer, Excluding Assessed Tax									(15,036)	(11,170)	(10,928)
Revenues									(15,036)	(11,170)	(10,928)
Intersegment Eliminations [Member] \| SemGas [Member]
Revenues									$ 15,036	$ 11,170	$ 10,928

Revenue Revenue (Details 2) $ in Thousands	Dec. 31, 2018 USD ($)
Period 1 [Member]
Revenue, Remaining Performance Obligation, Amount	$ 280,984
Period 2 [Member]
Revenue, Remaining Performance Obligation, Amount	227,981
Period 3 [Member]
Revenue, Remaining Performance Obligation, Amount	186,465
Period 4 [Member]
Revenue, Remaining Performance Obligation, Amount	169,252
Period 5 [Member]
Revenue, Remaining Performance Obligation, Amount	163,193
Thereafter [Member]
Revenue, Remaining Performance Obligation, Amount	$ 1,349,773

Revenue Revenue (Details 3) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Revenue from Contract with Customer [Abstract]
Contract with Customer, Asset, Net, Noncurrent	$ 11,496	$ 0

Revenue Revenue (Details Textual) $ in Millions	12 Months Ended
Revenue Revenue (Details Textual) $ in Millions	Dec. 31, 2018 USD ($)
Revenue from Contract with Customer [Abstract]
Deferred Revenue, Revenue Recognized	$ 4.2
Capitalized Contract Cost, Net	$ 9.4
capitalized contract costs amortization period	25 years
Capitalized Contract Cost, Amortization	$ 0.4

Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Basic earnings per share
Net income (loss)	$ 2,972	$ 8,461	$ (2,726)	$ (33,035)	$ 2,619	$ (19,103)	$ 9,611	$ (10,277)	$ (24,328)	$ (17,150)	$ 13,262
less: Income attributable to noncontrolling interest	2,421	0	0	0					2,421	0	11,167
Net income (loss) attributable to SemGroup	551	8,461	(2,726)	(33,035)					(26,749)	(17,150)	2,095
Preferred Stock Dividends, Income Statement Impact	6,430	6,317	6,211	4,832					23,790	0	0
Net Income (Loss) Available to Common Stockholders, Basic	$ (5,879)	$ 2,144	$ (8,937)	$ (37,867)					$ (50,539)	$ (17,150)	$ 2,095
Weighted average common stock outstanding									78,313	71,418	51,889
Earnings Per Share, Basic	$ (0.08)	$ 0.03	$ (0.11)	$ (0.48)	$ 0.03	$ (0.25)	$ 0.15	$ (0.16)	$ (0.65)	$ (0.24)	$ 0.04
Continuing Operations [Member]
Basic earnings per share
Net income (loss)									$ (24,328)	$ (17,150)	$ 13,263
less: Income attributable to noncontrolling interest									2,421	0	11,167
Net income (loss) attributable to SemGroup									(26,749)	$ (17,150)	$ 2,096
Preferred Stock Dividends, Income Statement Impact									23,790
Net Income (Loss) Available to Common Stockholders, Basic									$ (50,539)
Weighted average common stock outstanding									78,313	71,418	51,889
Earnings Per Share, Basic									$ (0.65)	$ (0.24)	$ 0.04
Discontinued Operations [Member]
Basic earnings per share
Net income (loss)									$ 0	$ 0	$ (1)
less: Income attributable to noncontrolling interest									0	0	0
Net income (loss) attributable to SemGroup									0	$ 0	$ (1)
Preferred Stock Dividends, Income Statement Impact									0
Net Income (Loss) Available to Common Stockholders, Basic									$ 0
Weighted average common stock outstanding									78,313	71,418	51,889
Earnings Per Share, Basic									$ 0	$ 0	$ 0

Earnings Per Share (Details 1) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Diluted earnings per share
Net income (loss)	$ 2,972	$ 8,461	$ (2,726)	$ (33,035)	$ 2,619	$ (19,103)	$ 9,611	$ (10,277)	$ (24,328)	$ (17,150)	$ 13,262
Less: net income attributable to noncontrolling interests	2,421	0	0	0					2,421	0	11,167
Net income (loss) attributable to SemGroup	551	8,461	(2,726)	(33,035)					(26,749)	(17,150)	2,095
Preferred Stock Dividends, Income Statement Impact	6,430	6,317	6,211	4,832					23,790	0	0
Net Income (Loss) Available to Common Stockholders, Basic	$ (5,879)	$ 2,144	$ (8,937)	$ (37,867)					$ (50,539)	$ (17,150)	$ 2,095
Weighted average common stock outstanding									78,313	71,418	51,889
Weighted Average Number Diluted Shares Outstanding Adjustment									0	0	392
Diluted weighted average common stock outstanding									78,313	71,418	52,281
Earnings Per Share, Diluted	$ (0.08)	$ 0.03	$ (0.11)	$ (0.48)	$ 0.03	$ (0.25)	$ 0.15	$ (0.16)	$ (0.65)	$ (0.24)	$ 0.04
Continuing Operations [Member]
Diluted earnings per share
Net income (loss)									$ (24,328)	$ (17,150)	$ 13,263
Less: net income attributable to noncontrolling interests									2,421	0	11,167
Net income (loss) attributable to SemGroup									(26,749)	$ (17,150)	$ 2,096
Preferred Stock Dividends, Income Statement Impact									23,790
Net Income (Loss) Available to Common Stockholders, Basic									$ (50,539)
Weighted average common stock outstanding									78,313	71,418	51,889
Weighted Average Number Diluted Shares Outstanding Adjustment									0	0	392
Diluted weighted average common stock outstanding									78,313	71,418	52,281
Earnings Per Share, Diluted									$ (0.65)	$ (0.24)	$ 0.04
Discontinued Operations [Member]
Diluted earnings per share
Net income (loss)									$ 0	$ 0	$ (1)
Less: net income attributable to noncontrolling interests									0	0	0
Net income (loss) attributable to SemGroup									0	$ 0	$ (1)
Preferred Stock Dividends, Income Statement Impact									0
Net Income (Loss) Available to Common Stockholders, Basic									$ 0
Weighted average common stock outstanding									78,313	71,418	51,889
Weighted Average Number Diluted Shares Outstanding Adjustment									0	0	392
Diluted weighted average common stock outstanding									78,313	71,418	52,281
Earnings Per Share, Diluted									$ 0	$ 0	$ 0

Earnings Per Share (Details Textual)	Dec. 31, 2018	Oct. 22, 2018
Earnings Per Share [Line Items]
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners	49.00%
Maurepas Pipeline LLC [Member]
Earnings Per Share [Line Items]
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners	49.00%	49.00%

Equity-Based Compensation (Details) - Restricted Stock [Member] - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award
Outstanding, shares	1,474,235	1,084,090	911,266	411,308
Awards granted, shares	781,100	377,766	702,309
Awards vested, shares	(202,545)	(149,961)	(168,096)
Awards forfeited, shares	(188,410)	(54,981)	(34,255)
Awards outstanding, average grant date fair value	$ 21.04	$ 29.07	$ 31.09	$ 75.25
Awards granted, average grant date fair value per share	22.10	35.22	19.18
Awards vested, average grant date fair value per share	$ 23.18	$ 33.60	$ 20.38
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Fair Value	$ 4,695	$ 5,039	$ 3,426
Awards forfeited, average grant date fair value per share	$ 49.72	$ 81.80	$ 42.42

Equity-Based Compensation (Details 1) - Restricted Stock [Member]	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Volatility Rate	54.20%	51.90%
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Risk Free Interest Rate	1.57%	0.98%

Equity-Based Compensation (Details 2) - Rose Rock Midstream L P [Member] - Restricted Stock Units (RSUs) [Member] - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Outstanding, shares	0	100,191
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Fair Value	$ 665
Awards outstanding, average grant date fair value	$ 0	$ 38.70
Awards granted, shares	117,204
Awards granted, average grant date fair value per share	$ 9.62
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period	57,458
Awards vested, average grant date fair value per share	$ 11.58
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period	1,846
Awards forfeited, average grant date fair value per share	$ 26.55
Rose Rock merger agreement [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Conversions Weighted Average Grant Date Fair Value	$ 19.57
Conversion of Stock, Shares Converted	158,091

Equity-Based Compensation (Details Textual) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unvested Dividend Equivalent Value	$ 2.7
Equity-based compensation expense recognized	11.4	$ 10.1	$ 8.8
Unrecognized compensation expense for nonvested awards	$ 13.9
Weighted average vesting period	16 months
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved for issuance pursuant to employee and director compensation programs	3,710,220
Shares paid for tax withholding	57,041	42,347	46,941
Awards granted, shares	781,100	377,766	702,309
Equity-based compensation awards which could vest if certain targets are met	558,000
Employee Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved for issuance pursuant to employee and director compensation programs	1,000,000
Employee stock purchase plan maximum contribution	10.00%
Share-based Compensation Arrangement by Share-based Payment Award, Purchase Price of Common Stock, Percent	85.00%
Stock Issued During Period, Shares, Employee Stock Purchase Plans	53,757	39,545	46,836
Rose Rock Midstream L P [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Equity-based compensation expense recognized			$ 1.2
Rose Rock Midstream L P [Member] \| Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares paid for tax withholding			254
Director [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Goods and Nonemployee Services Transaction, Securities Issued	0		2,676
Rose Rock merger agreement [Member] \| Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards granted, shares			128,585

Segments (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
Segments (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting Information
Revenues	$ 611,863	$ 633,996	$ 595,794	$ 661,609	$ 606,806	$ 545,922	$ 473,089	$ 456,100	$ 2,503,262	$ 2,081,917	$ 1,332,164
Income (Loss) from Equity Method Investments and Issuance of Common Units by Equity Method Investee									57,672	67,331	73,716
Depreciation, Depletion and Amortization									(209,254)	(158,421)	(98,804)
Income Tax Expense (Benefit)	6,531	(2,697)	(3,613)	23,083	31,141	(37,249)	3,625	95	23,304	(2,388)	11,268
Segment profit									467,549	406,523	350,096
EBITDA Adjustment to Equity Earnings									19,532	26,890	28,757
Net unrealized (gain) loss related to derivative instruments									(5,053)	40	989
General and Administrative Expense									91,568	113,779	84,183
Loss (gain) on disposal or impairment	(1,438)	(383)	1,824	(3,566)	(30,468)	41,625	(234)	2,410	(3,563)	13,333	16,048
Interest expense									149,714	103,009	62,650
Loss on early extinguishment of debt									0	19,930	0
Foreign currency transaction loss (gain)									9,501	(4,709)	4,759
Loss on sale or impairment of non-operated equity method investment									0	0	30,644
Other expense (income), net									(2,380)	(4,632)	(1,269)
Loss from Discontinued Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest									0	0	1
Net income (loss)	2,972	$ 8,461	$ (2,726)	$ (33,035)	2,619	$ (19,103)	$ 9,611	$ (10,277)	(24,328)	(17,150)	13,262
Additions to long-lived assets									370,536	2,521,080	324,681
Total assets	5,210,307				5,376,817				5,210,307	5,376,817
Equity method investments	274,009				285,281				274,009	285,281
U.S. Liquids [Member]
Segment Reporting Information
Revenues									2,017,701	1,493,548	827,379
Income (Loss) from Equity Method Investments and Issuance of Common Units by Equity Method Investee									57,625	67,345	71,569
U.S. Gas [Member]
Segment Reporting Information
Revenues									250,285	222,048	208,042
Canada [Member]
Segment Reporting Information
Revenues									193,134	183,232	133,216
Operating Segments [Member] \| U.S. Liquids [Member]
Segment Reporting Information
Depreciation, Depletion and Amortization									(142,237)	(88,738)	(32,449)
Income Tax Expense (Benefit)									575	362	0
Segment profit									309,423	229,208	190,768
Additions to long-lived assets									119,064	2,289,218	240,242
Total assets	3,689,384				3,871,334				3,689,384	3,871,334
Equity method investments	255,043				266,362				255,043	266,362
Operating Segments [Member] \| U.S. Gas [Member]
Segment Reporting Information
Depreciation, Depletion and Amortization									(42,997)	(37,059)	(36,170)
Segment profit									67,070	67,805	66,530
Additions to long-lived assets									31,102	100,537	21,913
Total assets	716,837				714,777				716,837	714,777
Operating Segments [Member] \| Canada [Member]
Segment Reporting Information
Depreciation, Depletion and Amortization									(21,051)	(18,530)	(16,867)
Income Tax Expense (Benefit)									11,018	8,863	3,667
Segment profit									81,330	76,274	53,264
Additions to long-lived assets									218,566	113,263	34,506
Total assets	684,418				518,900				684,418	518,900
Intersegment Eliminations [Member]
Segment Reporting Information
Revenues									(15,036)	(11,170)	(10,928)
Intersegment Eliminations [Member] \| U.S. Gas [Member]
Segment Reporting Information
Revenues									15,036	11,170	10,928
Corporate, Non-Segment [Member]
Segment Reporting Information
Revenues									42,142	183,089	163,527
Income (Loss) from Equity Method Investments and Issuance of Common Units by Equity Method Investee									47	(14)	2,147
Depreciation, Depletion and Amortization									(2,969)	(14,094)	(13,318)
Income Tax Expense (Benefit)									11,711	(11,613)	7,601
Segment profit									9,726	33,236	39,534
Additions to long-lived assets									1,804	18,062	$ 28,020
Total assets	119,668				271,806				119,668	271,806
Equity method investments	$ 18,966				$ 18,919				$ 18,966	$ 18,919

Supplemental Cash Flow Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Components of operating assets and liabilities
Increase (Decrease) in Restricted Cash	$ (33)	$ 1	$ 1
Decrease (increase) in accounts receivable	78,624	(237,394)	(90,810)
Decrease (increase) in receivable from affiliates	685	23,764	(19,541)
Decrease (increase) in inventories	52,166	(17,862)	(30,686)
Decrease (increase) in other current assets	(3,406)	2,947	634
Increase (decrease) in other noncurrent assets	1,636	14,307	297
Increase (decrease) in accounts payable and accrued liabilities	(78,829)	209,982	94,687
Increase (decrease) in payable to affiliates	(3,198)	(19,537)	21,475
Increase (decrease) in other noncurrent liabilities	1,374	19,385	2,573
Total changes in operating assets and liabilities	$ 45,813	$ (33,023)	$ (21,966)

Supplemental Cash Flow Information (Details Textual) - USD ($) $ in Millions		12 Months Ended
	Sep. 30, 2016	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Other Significant Noncash Transactions [Line Items]
Interest Paid, Including Capitalized Interest, Operating and Investing Activities		$ 141.2	$ 82.0	$ 71.3
Income taxes (net of refunds received)		16.8	7.2	0.7
Capital Expenditures Incurred but Not yet Paid		51.3	76.1	1.4
Insurance prepayment financed [Member]
Other Significant Noncash Transactions [Line Items]
Liabilities Assumed		$ 8.0	$ 6.2	$ 4.7
Rose Rock Midstream L P [Member]
Other Significant Noncash Transactions [Line Items]
Income Tax Effects Allocated Directly to Equity, Equity Transactions	$ (143.3)

Quarterly Financial Data (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Quarterly Financial Data [Line Items]
Revenues	$ 611,863	$ 633,996	$ 595,794	$ 661,609	$ 606,806	$ 545,922	$ 473,089	$ 456,100	$ 2,503,262	$ 2,081,917	$ 1,332,164
Loss (gain) on disposal or impairment	(1,438)	(383)	1,824	(3,566)	(30,468)	41,625	(234)	2,410	(3,563)	13,333	16,048
Costs and expenses excluding gains and losses on disposal or impairment	579,567	609,208	576,975	642,936	579,147	549,442	465,874	447,392	2,408,686	2,041,855
Total expenses	578,129	608,825	578,799	639,370	548,679	591,067	465,640	449,802	2,405,123	2,055,188	1,284,565
Earnings from equity method investments	16,179	14,528	14,351	12,614	15,120	17,367	17,753	17,091	57,672	67,331	73,757
Operating income	49,913	39,699	31,346	34,853	73,247	(27,778)	25,202	23,389	155,811	94,060	121,315
Interest and non-operating income (expense)	40,410	33,935	37,685	44,805	39,487	28,574	11,966	33,571	156,835	113,598	96,784
Income (loss) from continuing operations before income taxes	9,503	5,764	(6,339)	(9,952)	33,760	(56,352)	13,236	(10,182)	(1,024)	(19,538)	24,531
Income Tax Expense (Benefit)	6,531	(2,697)	(3,613)	23,083	31,141	(37,249)	3,625	95	23,304	(2,388)	11,268
Net income (loss)	2,972	8,461	(2,726)	(33,035)	$ 2,619	$ (19,103)	$ 9,611	$ (10,277)	(24,328)	(17,150)	13,262
Less: net income attributable to noncontrolling interests	2,421	0	0	0					2,421	0	11,167
Net income (loss) attributable to SemGroup	551	8,461	(2,726)	(33,035)					(26,749)	(17,150)	2,095
Preferred Stock Dividends, Income Statement Impact	6,430	6,317	6,211	4,832					23,790	0	0
Net Income (Loss) Available to Common Stockholders, Basic	$ (5,879)	$ 2,144	$ (8,937)	$ (37,867)					$ (50,539)	$ (17,150)	$ 2,095
Earnings Per Share, Basic	$ (0.08)	$ 0.03	$ (0.11)	$ (0.48)	$ 0.03	$ (0.25)	$ 0.15	$ (0.16)	$ (0.65)	$ (0.24)	$ 0.04
Earnings Per Share, Diluted	$ (0.08)	$ 0.03	$ (0.11)	$ (0.48)	$ 0.03	$ (0.25)	$ 0.15	$ (0.16)	$ (0.65)	$ (0.24)	$ 0.04

Quarterly Financial Data Quarterly Financial Data (Details Textual) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017
U.S. Liquids [Member]
Goodwill, Impairment Loss				$ 26,628
Impairment of Intangible Assets, Finite-lived				12,087
Kansas gas gathering and compression assets [Member] \| Disposal Group, Disposed of by Sale, Not Discontinued Operations [Member]
Gain (loss) on disposal		$ 4,500
Sem Mexico [Member]
Gain (loss) on disposal			$ 1,600
Sem Mexico [Member] \| Disposal Group, Held-for-sale, Not Discontinued Operations [Member]
Impairment of Long-Lived Assets to be Disposed of	$ 13,500			13,511
Sem Logistics [Member]
Gain (loss) on disposal			400
Sem Logistics [Member] \| Disposal Group, Held-for-sale, Not Discontinued Operations [Member]
Impairment of Long-Lived Assets to be Disposed of	$ 76,700			76,661
Glass Mountain Pipeline Llc [Member]
Equity Method Investment, Realized Gain (Loss) on Disposal			$ 1,100	$ 150,266

Related Party Transactions (Details) - Equity Method Investee [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
NGL Energy [Member]
Related Party Transaction
Revenues from related party	$ 18,168	$ 45,918	$ 61,639
Purchases from related party	681	29,695	57,739
White Cliffs Pipeline, LLC [Member]
Related Party Transaction
Purchases from related party	6,201	11,870	4,758
White Cliffs Pipeline, LLC [Member] \| Crude Oil Revenue [Member]
Related Party Transaction
Revenues from related party	0	436	4,973
White Cliffs Pipeline, LLC [Member] \| Storage Revenue [Member]
Related Party Transaction
Revenues from related party	4,350	4,350	4,350
White Cliffs Pipeline, LLC [Member] \| Transportation Fees [Member]
Related Party Transaction
Related Party Transaction, Expenses from Transactions with Related Party	12,506	11,298	10,797
White Cliffs Pipeline, LLC [Member] \| Management Fees [Member]
Related Party Transaction
Related Party Transaction, Expenses from Transactions with Related Party	$ 545	$ 519	$ 494

Related Party Transactions (Details Textual)	Dec. 31, 2018
White Cliffs Pipeline, LLC [Member]
Related Party Transaction [Line Items]
Equity method investment, ownership percentage	51.00%

Condensed Consolidating Guarantor Financial Statements Balance Sheet (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash and cash equivalents	$ 86,655	$ 93,699	$ 74,216	$ 58,096
Accounts Receivable, net	562,214	653,484
Receivable from affiliates	295	1,691
Current assets held for sale	0	38,063
Inventories	49,397	101,665
Other current assets	17,264	14,297
Total current assets	715,825	902,899
Property, plant and equipment	3,457,326	3,315,131
Equity method investments	274,009	285,281
Goodwill	257,302	257,302	34,230	48,032
Other intangible assets (net of accumulated amortization of $90,014 and $56,409, respectively)	365,038	398,643	150,978	162,223
Other Assets, Noncurrent	140,807	132,600
Noncurrent assets held for sale	0	84,961
Total assets	5,210,307	5,376,817
Accounts payable	494,792	587,898
Payable to affiliates	3,715	6,971
Accrued liabilities	115,095	131,407
Current liabilities held for sale	0	23,847
Other Liabilities, Current	23,555	16,438
Total current liabilities	637,157	766,561
Long-term debt	2,278,834	2,853,095
Deferred income taxes	55,789	46,585
Other noncurrent liabilities	38,548	38,495
Noncurrent liabilities held for sale	0	13,716
Commitments and contingencies
Redeemable preferred stock, $0.01 par value, $367,360 liquidation preference (authorized - 4,000 shares; issued - 350 and 0 shares, respectively)	359,658	0
Stockholders' Equity Attributable to Parent	1,490,832	1,658,365
Stockholders' Equity Attributable to Noncontrolling Interest	349,489	0
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	1,840,321	1,658,365	1,445,965	1,196,356
Liabilities and Equity	5,210,307	5,376,817
Reportable Legal Entities [Member] \| Parent Company [Member]
Cash and cash equivalents	40,064	32,457	19,002	4,559
Accounts Receivable, net	83	(9)
Receivable from affiliates	120	58
Current assets held for sale		0
Inventories	0	0
Other current assets	6,682	6,671
Total current assets	46,949	39,177
Property, plant and equipment	6,732	8,086
Equity method investments	3,267,581	3,085,274
Goodwill	0	0
Other intangible assets (net of accumulated amortization of $90,014 and $56,409, respectively)	5	10
Other Assets, Noncurrent	41,981	45,587
Noncurrent assets held for sale		0
Total assets	3,363,248	3,178,134
Accounts payable	38	646
Payable to affiliates	1	10
Accrued liabilities	33,239	38,747
Current liabilities held for sale		0
Other Liabilities, Current	5,723	1,922
Total current liabilities	39,001	41,325
Long-term debt	1,467,083	1,474,491
Deferred income taxes	4,882	1,892
Other noncurrent liabilities	1,792	2,061
Noncurrent liabilities held for sale		0
Commitments and contingencies
Redeemable preferred stock, $0.01 par value, $367,360 liquidation preference (authorized - 4,000 shares; issued - 350 and 0 shares, respectively)	359,658
Stockholders' Equity Attributable to Parent	1,490,832
Stockholders' Equity Attributable to Noncontrolling Interest	0
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	1,490,832	1,658,365
Liabilities and Equity	3,363,248	3,178,134
Reportable Legal Entities [Member] \| Guarantor Subsidiaries [Member]
Cash and cash equivalents	0	0	0	9,058
Accounts Receivable, net	461,980	562,967
Receivable from affiliates	18	1,421
Current assets held for sale		0
Inventories	49,397	101,665
Other current assets	6,711	4,493
Total current assets	518,106	670,546
Property, plant and equipment	992,974	1,002,982
Equity method investments	1,553,360	2,110,299
Goodwill	0	0
Other intangible assets (net of accumulated amortization of $90,014 and $56,409, respectively)	119,583	127,783
Other Assets, Noncurrent	4,788	3,097
Noncurrent assets held for sale		0
Total assets	3,188,811	3,914,707
Accounts payable	444,984	533,651
Payable to affiliates	3,714	6,961
Accrued liabilities	18,424	26,092
Current liabilities held for sale		0
Other Liabilities, Current	3,409	5,532
Total current liabilities	470,531	572,236
Long-term debt	6,315	572,558
Deferred income taxes	0	0
Other noncurrent liabilities	0	0
Noncurrent liabilities held for sale		0
Commitments and contingencies
Redeemable preferred stock, $0.01 par value, $367,360 liquidation preference (authorized - 4,000 shares; issued - 350 and 0 shares, respectively)	0
Stockholders' Equity Attributable to Parent	2,711,965
Stockholders' Equity Attributable to Noncontrolling Interest	0
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	2,711,965	2,769,913
Liabilities and Equity	3,188,811	3,914,707
Reportable Legal Entities [Member] \| Non-Guarantor Subsidiaries [Member]
Cash and cash equivalents	50,742	69,872	59,796	46,043
Accounts Receivable, net	100,151	90,526
Receivable from affiliates	157	212
Current assets held for sale		38,063
Inventories	0	0
Other current assets	3,871	3,133
Total current assets	154,921	201,806
Property, plant and equipment	2,457,620	2,304,063
Equity method investments	0	0
Goodwill	257,302	257,302
Other intangible assets (net of accumulated amortization of $90,014 and $56,409, respectively)	245,450	270,850
Other Assets, Noncurrent	94,038	83,916
Noncurrent assets held for sale		84,961
Total assets	3,209,331	3,202,898
Accounts payable	49,770	53,601
Payable to affiliates	0	0
Accrued liabilities	63,430	66,570
Current liabilities held for sale		23,847
Other Liabilities, Current	14,423	8,984
Total current liabilities	127,623	153,002
Long-term debt	811,751	829,236
Deferred income taxes	50,907	44,693
Other noncurrent liabilities	36,756	36,434
Noncurrent liabilities held for sale		13,716
Commitments and contingencies
Redeemable preferred stock, $0.01 par value, $367,360 liquidation preference (authorized - 4,000 shares; issued - 350 and 0 shares, respectively)	0
Stockholders' Equity Attributable to Parent	1,832,805
Stockholders' Equity Attributable to Noncontrolling Interest	349,489
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	2,182,294	2,125,817
Liabilities and Equity	3,209,331	3,202,898
Consolidation, Eliminations [Member]
Cash and cash equivalents	(4,151)	(8,630)	$ (4,582)	$ (1,564)
Accounts Receivable, net	0	0
Receivable from affiliates	0	0
Current assets held for sale		0
Inventories	0	0
Other current assets	0	0
Total current assets	(4,151)	(8,630)
Property, plant and equipment	0	0
Equity method investments	(4,546,932)	(4,910,292)
Goodwill	0	0
Other intangible assets (net of accumulated amortization of $90,014 and $56,409, respectively)	0	0
Other Assets, Noncurrent	0	0
Noncurrent assets held for sale		0
Total assets	(4,551,083)	(4,918,922)
Accounts payable	0	0
Payable to affiliates	0	0
Accrued liabilities	2	(2)
Current liabilities held for sale		0
Other Liabilities, Current	0	0
Total current liabilities	2	(2)
Long-term debt	(6,315)	(23,190)
Deferred income taxes	0	0
Other noncurrent liabilities	0	0
Noncurrent liabilities held for sale		0
Commitments and contingencies
Redeemable preferred stock, $0.01 par value, $367,360 liquidation preference (authorized - 4,000 shares; issued - 350 and 0 shares, respectively)	0
Stockholders' Equity Attributable to Parent	(4,544,770)
Stockholders' Equity Attributable to Noncontrolling Interest	0
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	(4,544,770)	(4,895,730)
Liabilities and Equity	$ (4,551,083)	$ (4,918,922)

Condensed Consolidating Guarantor Financial Statements Condensed Consolidating Guarantor Financial Statements Statement of Operations (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Direct Financing Lease, Revenue									$ 17,549	$ 5,843	$ 0
Revenues	$ 611,863	$ 633,996	$ 595,794	$ 661,609	$ 606,806	$ 545,922	$ 473,089	$ 456,100	2,503,262	2,081,917	1,332,164
Costs of products sold, exclusive of depreciation and amortization shown below									1,823,095	1,514,891	873,431
Operating Costs and Expenses									284,769	254,764	212,099
General and Administrative Expense									91,568	113,779	84,183
Depreciation, Depletion and Amortization									209,254	158,421	98,804
Loss (gain) on disposal or impairment	(1,438)	(383)	1,824	(3,566)	(30,468)	41,625	(234)	2,410	(3,563)	13,333	16,048
Costs and Expenses	578,129	608,825	578,799	639,370	548,679	591,067	465,640	449,802	2,405,123	2,055,188	1,284,565
Earnings from equity method investments	16,179	14,528	14,351	12,614	15,120	17,367	17,753	17,091	57,672	67,331	73,757
Loss on issuance of common units by equity method investee									0	0	(41)
Operating Income (Loss)	49,913	39,699	31,346	34,853	73,247	(27,778)	25,202	23,389	155,811	94,060	121,315
Interest Expense									149,714	103,009	62,650
Loss on early extinguishment of debt									0	19,930	0
Foreign Currency Transaction Gain (Loss), before Tax									9,501	(4,709)	4,759
Loss on sale or impairment of non-operated equity method investment									0	0	30,644
Other Nonoperating Income (Expense)									(2,380)	(4,632)	(1,269)
Interest and non-operating income (expense)	40,410	33,935	37,685	44,805	39,487	28,574	11,966	33,571	156,835	113,598	96,784
Income (loss) from continuing operations before income taxes	9,503	5,764	(6,339)	(9,952)	33,760	(56,352)	13,236	(10,182)	(1,024)	(19,538)	24,531
Income tax expense (benefit)	6,531	(2,697)	(3,613)	23,083	31,141	(37,249)	3,625	95	23,304	(2,388)	11,268
Income (Loss) from Continuing Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest									(24,328)	(17,150)	13,263
Income (Loss) from Discontinued Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest									0	0	(1)
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	2,972	8,461	(2,726)	(33,035)	$ 2,619	$ (19,103)	$ 9,611	$ (10,277)	(24,328)	(17,150)	13,262
Less: net income attributable to noncontrolling interests	2,421	0	0	0					2,421	0	11,167
Net income (loss) attributable to SemGroup	551	8,461	(2,726)	(33,035)					(26,749)	(17,150)	2,095
Preferred Stock Dividends, Income Statement Impact	6,430	6,317	6,211	4,832					23,790	0	0
Net Income (Loss) Available to Common Stockholders, Basic	$ (5,879)	$ 2,144	$ (8,937)	$ (37,867)					(50,539)	(17,150)	2,095
Other Comprehensive Income (Loss), Net of Tax									2,554	20,113	(15,352)
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest									(21,774)	2,963	(2,090)
Comprehensive Income (Loss), Net of Tax, Attributable to Noncontrolling Interest									2,421	0	11,167
Comprehensive Income (Loss), Net of Tax, Attributable to Parent									(24,195)	2,963	(13,257)
Reportable Legal Entities [Member] \| Parent Company [Member]
Direct Financing Lease, Revenue									0	0
Revenues									0	0	0
Costs of products sold, exclusive of depreciation and amortization shown below									0	0	0
Operating Costs and Expenses									0	0	0
General and Administrative Expense									23,580	42,422	22,349
Depreciation, Depletion and Amortization									2,890	2,294	1,647
Loss (gain) on disposal or impairment									133,053	0	0
Costs and Expenses									159,523	44,716	23,996
Earnings from equity method investments									219,181	68,964	56,815
Loss on issuance of common units by equity method investee											(41)
Operating Income (Loss)									59,658	24,248	32,778
Interest Expense									68,389	40,053	(4,002)
Loss on early extinguishment of debt										19,930
Foreign Currency Transaction Gain (Loss), before Tax									10,246	(2,764)	0
Loss on sale or impairment of non-operated equity method investment											30,644
Other Nonoperating Income (Expense)									(976)	(913)	(339)
Interest and non-operating income (expense)									77,659	56,306	26,303
Income (loss) from continuing operations before income taxes									(18,001)	(32,058)	6,475
Income tax expense (benefit)									8,748	(14,908)	4,380
Income (Loss) from Continuing Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest										(17,150)	2,095
Income (Loss) from Discontinued Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest											0
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest									(26,749)	(17,150)	2,095
Less: net income attributable to noncontrolling interests									0
Net income (loss) attributable to SemGroup									(26,749)		2,095
Net Income (Loss) Available to Common Stockholders, Basic									(50,539)
Other Comprehensive Income (Loss), Net of Tax									(9,420)	(11,987)	7,360
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest									(36,169)	(29,137)	9,455
Comprehensive Income (Loss), Net of Tax, Attributable to Noncontrolling Interest									0		0
Comprehensive Income (Loss), Net of Tax, Attributable to Parent									(36,169)		9,455
Reportable Legal Entities [Member] \| Guarantor Subsidiaries [Member]
Direct Financing Lease, Revenue									0	0
Revenues									2,016,375	1,617,951	1,035,421
Costs of products sold, exclusive of depreciation and amortization shown below									1,796,716	1,383,868	761,971
Operating Costs and Expenses									110,795	112,863	115,431
General and Administrative Expense									24,742	24,492	31,196
Depreciation, Depletion and Amortization									76,788	70,053	68,669
Loss (gain) on disposal or impairment									(154,302)	70,681	16,115
Costs and Expenses									1,854,739	1,661,957	993,382
Earnings from equity method investments									73,010	(21,499)	81,366
Loss on issuance of common units by equity method investee											0
Operating Income (Loss)									234,646	(65,505)	123,405
Interest Expense									56,217	55,119	72,277
Loss on early extinguishment of debt										0
Foreign Currency Transaction Gain (Loss), before Tax									147	0	0
Loss on sale or impairment of non-operated equity method investment											0
Other Nonoperating Income (Expense)									(138)	(33)	63
Interest and non-operating income (expense)									56,226	55,086	72,340
Income (loss) from continuing operations before income taxes									178,420	(120,591)	51,065
Income tax expense (benefit)									0	0	0
Income (Loss) from Continuing Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest										(120,591)	51,065
Income (Loss) from Discontinued Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest											0
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest									178,420	(120,591)	51,065
Less: net income attributable to noncontrolling interests									0		11,167
Net income (loss) attributable to SemGroup									178,420		39,898
Preferred Stock Dividends, Income Statement Impact									0
Net Income (Loss) Available to Common Stockholders, Basic									178,420
Other Comprehensive Income (Loss), Net of Tax									387	(573)	1,223
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest									178,807	(121,164)	52,288
Comprehensive Income (Loss), Net of Tax, Attributable to Noncontrolling Interest									0		11,167
Comprehensive Income (Loss), Net of Tax, Attributable to Parent									178,807		41,121
Reportable Legal Entities [Member] \| Non-Guarantor Subsidiaries [Member]
Direct Financing Lease, Revenue									17,549	5,843
Revenues									486,887	463,966	296,743
Costs of products sold, exclusive of depreciation and amortization shown below									26,379	131,023	111,460
Operating Costs and Expenses									173,974	141,901	96,668
General and Administrative Expense									43,246	46,865	30,638
Depreciation, Depletion and Amortization									129,576	86,074	28,488
Loss (gain) on disposal or impairment									17,686	(57,348)	(67)
Costs and Expenses									390,861	348,515	267,187
Earnings from equity method investments									0	7,494	0
Loss on issuance of common units by equity method investee											0
Operating Income (Loss)									96,026	122,945	29,556
Interest Expense									25,348	8,691	(4,819)
Loss on early extinguishment of debt										0
Foreign Currency Transaction Gain (Loss), before Tax									(892)	(1,945)	4,759
Loss on sale or impairment of non-operated equity method investment											0
Other Nonoperating Income (Expense)									(1,506)	(4,540)	(1,799)
Interest and non-operating income (expense)									22,950	2,206	(1,859)
Income (loss) from continuing operations before income taxes									73,076	120,739	31,415
Income tax expense (benefit)									14,556	12,520	6,888
Income (Loss) from Continuing Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest										108,219	24,527
Income (Loss) from Discontinued Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest											(1)
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest									58,520	108,219	24,526
Net income (loss) attributable to SemGroup									56,099		24,526
Preferred Stock Dividends, Income Statement Impact									0
Net Income (Loss) Available to Common Stockholders, Basic									56,099
Other Comprehensive Income (Loss), Net of Tax									11,587	32,673	(23,935)
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest									70,107	140,892	591
Comprehensive Income (Loss), Net of Tax, Attributable to Noncontrolling Interest									2,421		0
Comprehensive Income (Loss), Net of Tax, Attributable to Parent									67,686		591
Consolidation, Eliminations [Member]
Direct Financing Lease, Revenue									0	0
Revenues									0	0	0
Costs of products sold, exclusive of depreciation and amortization shown below									0	0	0
Operating Costs and Expenses									0	0	0
General and Administrative Expense									0	0	0
Depreciation, Depletion and Amortization									0	0	0
Loss (gain) on disposal or impairment									0	0	0
Costs and Expenses									0	0	0
Earnings from equity method investments									(234,519)	12,372	(64,424)
Loss on issuance of common units by equity method investee											0
Operating Income (Loss)									(234,519)	12,372	(64,424)
Interest Expense									(240)	(854)	(806)
Loss on early extinguishment of debt										0
Foreign Currency Transaction Gain (Loss), before Tax									0	0	0
Loss on sale or impairment of non-operated equity method investment											0
Other Nonoperating Income (Expense)									240	854	806
Interest and non-operating income (expense)									0	0	0
Income (loss) from continuing operations before income taxes									(234,519)	12,372	(64,424)
Income tax expense (benefit)									0	0	0
Income (Loss) from Continuing Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest										12,372	(64,424)
Income (Loss) from Discontinued Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest											0
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest									(234,519)	12,372	(64,424)
Less: net income attributable to noncontrolling interests									0
Net income (loss) attributable to SemGroup									(234,519)		(64,424)
Preferred Stock Dividends, Income Statement Impact									0
Net Income (Loss) Available to Common Stockholders, Basic									(234,519)
Other Comprehensive Income (Loss), Net of Tax									0	0	0
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest									(234,519)	12,372	(64,424)
Comprehensive Income (Loss), Net of Tax, Attributable to Noncontrolling Interest									0		0
Comprehensive Income (Loss), Net of Tax, Attributable to Parent									(234,519)		(64,424)
Service [Member]
Revenue from Contract with Customer, Excluding Assessed Tax									518,764	391,266	265,030
Service [Member] \| Reportable Legal Entities [Member] \| Parent Company [Member]
Revenue from Contract with Customer, Excluding Assessed Tax									0	0	0
Service [Member] \| Reportable Legal Entities [Member] \| Guarantor Subsidiaries [Member]
Revenue from Contract with Customer, Excluding Assessed Tax									140,275	149,197	162,460
Service [Member] \| Reportable Legal Entities [Member] \| Non-Guarantor Subsidiaries [Member]
Revenue from Contract with Customer, Excluding Assessed Tax									378,489	242,069	102,570
Service [Member] \| Consolidation, Eliminations [Member]
Revenue from Contract with Customer, Excluding Assessed Tax									0	0	0
Other revenue [Member]
Revenue from Contract with Customer, Excluding Assessed Tax									59,513	62,890	57,725
Other revenue [Member] \| Reportable Legal Entities [Member] \| Parent Company [Member]
Revenue from Contract with Customer, Excluding Assessed Tax									0	0	0
Other revenue [Member] \| Reportable Legal Entities [Member] \| Guarantor Subsidiaries [Member]
Revenue from Contract with Customer, Excluding Assessed Tax									0	0	0
Other revenue [Member] \| Reportable Legal Entities [Member] \| Non-Guarantor Subsidiaries [Member]
Revenue from Contract with Customer, Excluding Assessed Tax									59,513	62,890	57,725
Other revenue [Member] \| Consolidation, Eliminations [Member]
Revenue from Contract with Customer, Excluding Assessed Tax									0	0	0
Product [Member]
Revenue from Contract with Customer, Excluding Assessed Tax									1,907,436	1,621,918	1,009,409
Product [Member] \| Reportable Legal Entities [Member] \| Parent Company [Member]
Revenue from Contract with Customer, Excluding Assessed Tax									0	0	0
Product [Member] \| Reportable Legal Entities [Member] \| Guarantor Subsidiaries [Member]
Revenue from Contract with Customer, Excluding Assessed Tax									1,876,100	1,468,754	872,961
Product [Member] \| Reportable Legal Entities [Member] \| Non-Guarantor Subsidiaries [Member]
Revenue from Contract with Customer, Excluding Assessed Tax									31,336	153,164	136,448
Product [Member] \| Consolidation, Eliminations [Member]
Revenue from Contract with Customer, Excluding Assessed Tax									$ 0	$ 0	$ 0

Condensed Consolidating Guarantor Financial Statements Condensed Consolidating Guarantor Financial Statements Statement of Cash Flows (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Net Cash Provided by (Used in) Operating Activities	$ 269,704	$ 140,476	$ 169,974
Payments to Acquire Property, Plant, and Equipment	390,734	462,713	312,456
Proceeds from sale of equity method investment and other long-lived assets	1,958	314,821	151
Payments to Acquire Equity Method Investments	7,781	26,444	4,188
Proceeds from Sale of Equity Method Investments	0	0	60,483
Payments to Acquire Businesses, Net of Cash Acquired	0	(294,239)	0
Proceeds from Divestiture of Businesses, Net of Cash Divested	147,787	0	0
Distributions from equity method investments in excess of equity in earnings	19,100	28,774	27,726
Net Cash Provided by (Used in) Investing Activities	(229,670)	(439,801)	(228,284)
Payments of Debt Issuance Costs	4,720	11,116	7,728
Borrowings on credit facilities and issuance of senior unsecured notes	1,258,500	1,525,377	382,500
Repayments of Long-term Debt, Long-term Capital Lease Obligations, and Capital Securities	1,839,894	1,052,428	396,890
Proceeds from Noncontrolling Interests	350,000	0	0
Payment for Debt Extinguishment or Debt Prepayment Cost	0	(16,293)	0
Proceeds from issuance of common shares, net of offering costs	0	0	223,025
Payments for Repurchase of Common Stock		1,473	965
Payments of Ordinary Dividends, Noncontrolling Interest	(2,932)	0	(32,133)
Proceeds from Issuance of Preferred Stock and Preference Stock	342,299	0	0
Payments Related to Tax Withholding for Share-based Compensation	705	1,473	965
Payments of Ordinary Dividends, Common Stock	148,482	129,925	92,910
Proceeds from issuance of common stock under employee stock purchase plan	930	1,114	1,010
Intercompany payments and receipts	0	0	0
Net Cash Provided by (Used in) Financing Activities	(45,004)	315,256	75,909
Effect of Exchange Rate on Cash and Cash Equivalents	(2,074)	3,552	(1,479)
Cash and Cash Equivalents, Period Increase (Decrease)	(7,044)	19,483	16,120
Cash and Cash Equivalents, at Carrying Value	86,655	93,699	74,216	$ 58,096
Reportable Legal Entities [Member] \| Parent Company [Member]
Net Cash Provided by (Used in) Operating Activities	(90,572)	(46,556)	84,460
Payments to Acquire Property, Plant, and Equipment	1,529	4,554	2,928
Proceeds from sale of equity method investment and other long-lived assets	0	0	0
Payments to Acquire Equity Method Investments	0	0	0
Proceeds from Sale of Equity Method Investments			60,483
Payments to Acquire Businesses, Net of Cash Acquired		0
Proceeds from Divestiture of Businesses, Net of Cash Divested	156,499
Distributions from equity method investments in excess of equity in earnings	0	0	0
Net Cash Provided by (Used in) Investing Activities	154,970	(4,554)	57,555
Payments of Debt Issuance Costs	475	11,116	7,728
Borrowings on credit facilities and issuance of senior unsecured notes	660,000	1,470,377	382,500
Repayments of Long-term Debt, Long-term Capital Lease Obligations, and Capital Securities	678,865	1,049,652	396,859
Proceeds from Noncontrolling Interests	350,000
Payment for Debt Extinguishment or Debt Prepayment Cost		(16,293)
Proceeds from issuance of common shares, net of offering costs			223,025
Payments for Repurchase of Common Stock		1,473	965
Payments of Ordinary Dividends, Noncontrolling Interest	(2,932)		0
Proceeds from Issuance of Preferred Stock and Preference Stock	342,299
Payments Related to Tax Withholding for Share-based Compensation	705
Payments of Ordinary Dividends, Common Stock	148,482	129,925	92,910
Proceeds from issuance of common stock under employee stock purchase plan	930	1,114	1,010
Intercompany payments and receipts	(578,561)	(198,467)	(235,645)
Net Cash Provided by (Used in) Financing Activities	(56,791)	64,565	(127,572)
Effect of Exchange Rate on Cash and Cash Equivalents	0	0	0
Cash and Cash Equivalents, Period Increase (Decrease)	7,607	13,455	14,443
Cash and Cash Equivalents, at Carrying Value	40,064	32,457	19,002	4,559
Reportable Legal Entities [Member] \| Guarantor Subsidiaries [Member]
Net Cash Provided by (Used in) Operating Activities	144,902	93,107	79,054
Payments to Acquire Property, Plant, and Equipment	65,798	135,999	56,102
Proceeds from sale of equity method investment and other long-lived assets	664	15,565	53
Payments to Acquire Equity Method Investments	7,781	2,888	4,188
Proceeds from Sale of Equity Method Investments			0
Payments to Acquire Businesses, Net of Cash Acquired		0
Proceeds from Divestiture of Businesses, Net of Cash Divested	6,753
Distributions from equity method investments in excess of equity in earnings	19,100	18,261	27,726
Net Cash Provided by (Used in) Investing Activities	(47,062)	(105,061)	(32,511)
Payments of Debt Issuance Costs	0	0	0
Borrowings on credit facilities and issuance of senior unsecured notes	0	0	0
Repayments of Long-term Debt, Long-term Capital Lease Obligations, and Capital Securities	565,904	26	31
Proceeds from Noncontrolling Interests	0
Payment for Debt Extinguishment or Debt Prepayment Cost		0
Proceeds from issuance of common shares, net of offering costs			0
Payments for Repurchase of Common Stock		0	0
Payments of Ordinary Dividends, Noncontrolling Interest	0		(32,133)
Proceeds from Issuance of Preferred Stock and Preference Stock	0
Payments Related to Tax Withholding for Share-based Compensation	0
Payments of Ordinary Dividends, Common Stock	0	0	0
Proceeds from issuance of common stock under employee stock purchase plan	0	0	0
Intercompany payments and receipts	468,079	11,980	(23,437)
Net Cash Provided by (Used in) Financing Activities	(97,825)	11,954	(55,601)
Effect of Exchange Rate on Cash and Cash Equivalents	(15)	0	0
Cash and Cash Equivalents, Period Increase (Decrease)	0	0	(9,058)
Cash and Cash Equivalents, at Carrying Value	0	0	0	9,058
Reportable Legal Entities [Member] \| Non-Guarantor Subsidiaries [Member]
Net Cash Provided by (Used in) Operating Activities	215,374	93,925	65,282
Payments to Acquire Property, Plant, and Equipment	323,407	322,160	253,426
Proceeds from sale of equity method investment and other long-lived assets	1,294	299,256	98
Payments to Acquire Equity Method Investments	0	23,556	0
Proceeds from Sale of Equity Method Investments			0
Payments to Acquire Businesses, Net of Cash Acquired		(294,239)
Proceeds from Divestiture of Businesses, Net of Cash Divested	(15,465)
Distributions from equity method investments in excess of equity in earnings	0	10,513	0
Net Cash Provided by (Used in) Investing Activities	(337,578)	(330,186)	(253,328)
Payments of Debt Issuance Costs	4,245	0	0
Borrowings on credit facilities and issuance of senior unsecured notes	598,500	55,000	0
Repayments of Long-term Debt, Long-term Capital Lease Obligations, and Capital Securities	595,125	2,750	0
Proceeds from Noncontrolling Interests	0
Payment for Debt Extinguishment or Debt Prepayment Cost		0
Proceeds from issuance of common shares, net of offering costs			0
Payments for Repurchase of Common Stock		0	0
Payments of Ordinary Dividends, Noncontrolling Interest	0		0
Proceeds from Issuance of Preferred Stock and Preference Stock	0
Payments Related to Tax Withholding for Share-based Compensation	0
Payments of Ordinary Dividends, Common Stock	0	0	0
Proceeds from issuance of common stock under employee stock purchase plan	0	0	0
Intercompany payments and receipts	106,003	190,535	203,278
Net Cash Provided by (Used in) Financing Activities	105,133	242,785	203,278
Effect of Exchange Rate on Cash and Cash Equivalents	(2,059)	3,552	(1,479)
Cash and Cash Equivalents, Period Increase (Decrease)	(19,130)	10,076	13,753
Cash and Cash Equivalents, at Carrying Value	50,742	69,872	59,796	46,043
Consolidation, Eliminations [Member]
Net Cash Provided by (Used in) Operating Activities	0	0	(58,822)
Payments to Acquire Property, Plant, and Equipment	0	0	0
Proceeds from sale of equity method investment and other long-lived assets	0	0	0
Payments to Acquire Equity Method Investments	0	0	0
Proceeds from Sale of Equity Method Investments			0
Payments to Acquire Businesses, Net of Cash Acquired		0
Proceeds from Divestiture of Businesses, Net of Cash Divested	0
Distributions from equity method investments in excess of equity in earnings	0	0	0
Net Cash Provided by (Used in) Investing Activities	0	0	0
Payments of Debt Issuance Costs	0	0	0
Borrowings on credit facilities and issuance of senior unsecured notes	0	0	0
Repayments of Long-term Debt, Long-term Capital Lease Obligations, and Capital Securities	0	0	0
Proceeds from Noncontrolling Interests	0
Payment for Debt Extinguishment or Debt Prepayment Cost		0
Proceeds from issuance of common shares, net of offering costs			0
Payments for Repurchase of Common Stock		0	0
Payments of Ordinary Dividends, Noncontrolling Interest	0		0
Proceeds from Issuance of Preferred Stock and Preference Stock	0
Payments Related to Tax Withholding for Share-based Compensation	0
Payments of Ordinary Dividends, Common Stock	0	0	0
Proceeds from issuance of common stock under employee stock purchase plan	0	0	0
Intercompany payments and receipts	4,479	(4,048)	55,804
Net Cash Provided by (Used in) Financing Activities	4,479	(4,048)	55,804
Effect of Exchange Rate on Cash and Cash Equivalents	0	0	0
Cash and Cash Equivalents, Period Increase (Decrease)	4,479	(4,048)	(3,018)
Cash and Cash Equivalents, at Carrying Value	$ (4,151)	$ (8,630)	$ (4,582)	$ (1,564)

Subsequent Events (Details) $ in Millions, $ in Millions	Feb. 25, 2019 USD ($) shares	Feb. 25, 2019 CAD ($)	Jan. 19, 2018 shares	Feb. 25, 2019 CAD ($) shares	Dec. 31, 2018 USD ($) shares	Dec. 31, 2017 shares
Preferred Stock, Shares Issued \| shares			350,000		350,000	0
Preferred Stock, Dividend Rate, Percentage			7.00%
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners					49.00%
Subsequent Event [Member] \| SemCAMS Midstream [Member]
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners	49.00%			49.00%
Noncontrolling Interest, Ownership Percentage by Parent	51.00%			51.00%
Subsequent Event [Member] \| Meritage ULC [Member]
Payments to Acquire Businesses, Gross	$ 489.5	$ 646.5
Reimbursement of Estimated Capital Expenditures	$ 115.5			$ 152.3
Business Acquisition, Percentage of Voting Interests Acquired	100.00%			100.00%
Subsequent Event [Member] \| SemCAMS Midstream [Member]
Business combination, contribution to joint venture by noncontrolling interest owner	$ 595.7			$ 785.6
Contribution to joint venture, potential contingent consideration payable, noncontrolling interest	$ 11.1			$ 14.7
Business Acquisition, Percentage of Voting Interests Acquired	51.00%			51.00%
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners	49.00%			49.00%
Semcams [Member] \| Subsequent Event [Member]
Equity contributed to joint venture	100.00%			100.00%
Proceeds from Divestiture of Businesses	$ 489.6	645.6
Contribution to joint venture, potential contingent consideration	11.1	14.7
Contribution to joint venture, contingent consideration, potential special share dividends	$ 37.9	$ 50.0
Noncontrolling Interest [Member] \| Subsequent Event [Member] \| SemCAMS Midstream [Member]
Preferred share conversion, percentage of IPO price	92.50%	92.50%
Preferred Stock, Shares Issued \| shares	300,000			300,000
Preferred Stock, Value, Issued	$ 227.5			$ 300.0
Preferred Stock, Dividend Rate, Percentage	8.75%	8.75%
Transaction fee paid to noncontrolling interest	$ 4.5			6.0
SemCAMS Midstream [Member] \| Subsequent Event [Member]
Limit on potential increase in facility				250.0
Revolving Credit Facility [Member]
Maximum borrowing capacity					$ 1,000.0
Revolving Credit Facility [Member] \| SemCAMS Midstream [Member] \| Subsequent Event [Member]
Maximum borrowing capacity				450.0
Term Loan B [Member] \| SemCAMS Midstream [Member] \| Subsequent Event [Member]
Long-term Debt, Gross				$ 350.0

Employee Benefit Plans Employee Benefit Plans (Details 1) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Plan with Accumulated Benefit Obligation in Excess of Plan Assets, Plan Assets	$ 39,197	$ 43,098
Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Plan with Accumulated Benefit Obligation in Excess of Plan Assets, Plan Assets	15,956	17,209
Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Plan with Accumulated Benefit Obligation in Excess of Plan Assets, Plan Assets	23,241	25,889
Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Plan with Accumulated Benefit Obligation in Excess of Plan Assets, Plan Assets	0	0
Cash and Cash Equivalents [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Plan with Accumulated Benefit Obligation in Excess of Plan Assets, Plan Assets	831	538
Cash and Cash Equivalents [Member] \| Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Plan with Accumulated Benefit Obligation in Excess of Plan Assets, Plan Assets	831	538
Cash and Cash Equivalents [Member] \| Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Plan with Accumulated Benefit Obligation in Excess of Plan Assets, Plan Assets	0	0
Cash and Cash Equivalents [Member] \| Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Plan with Accumulated Benefit Obligation in Excess of Plan Assets, Plan Assets	0	0
Mutual Fund [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Plan with Accumulated Benefit Obligation in Excess of Plan Assets, Plan Assets	15,125	16,671
Mutual Fund [Member] \| Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Plan with Accumulated Benefit Obligation in Excess of Plan Assets, Plan Assets	15,125	16,671
Mutual Fund [Member] \| Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Plan with Accumulated Benefit Obligation in Excess of Plan Assets, Plan Assets	0	0
Mutual Fund [Member] \| Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Plan with Accumulated Benefit Obligation in Excess of Plan Assets, Plan Assets	0	0
Fixed Income Funds [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Plan with Accumulated Benefit Obligation in Excess of Plan Assets, Plan Assets	23,241	25,889
Fixed Income Funds [Member] \| Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Plan with Accumulated Benefit Obligation in Excess of Plan Assets, Plan Assets	0	0
Fixed Income Funds [Member] \| Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Plan with Accumulated Benefit Obligation in Excess of Plan Assets, Plan Assets	23,241	25,889
Fixed Income Funds [Member] \| Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Plan with Accumulated Benefit Obligation in Excess of Plan Assets, Plan Assets	$ 0	$ 0