Consolidated Statements of Operations and Comprehensive Income (Loss) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenues:
Product									$ 1,621,918	$ 1,009,409	$ 1,118,886
Service									391,266	265,030	259,542
Lease									5,843	0	0
Other									62,890	57,725	76,666
Total revenues	$ 606,806	$ 545,922	$ 473,089	$ 456,100	$ 402,172	$ 327,764	$ 287,377	$ 314,851	2,081,917	1,332,164	1,455,094
Costs of products sold, exclusive of depreciation and amortization shown below									1,514,891	873,431	979,549
Expenses:
Operating									254,764	212,099	224,443
General and administrative									110,373	83,908	97,366
Depreciation and amortization									158,421	98,804	100,882
Loss on disposal or impairment, net (Note 4)	(30,468)	41,625	(234)	2,410	38	1,018	1,685	13,307	13,333	16,048	11,472
Total expenses	548,587	587,888	465,573	449,734	382,007	317,662	279,064	305,557	2,051,782	1,284,290	1,413,712
Earnings from equity method investments	15,120	17,367	17,753	17,091	17,763	15,845	17,078	23,071	67,331	73,757	81,386
Gain (loss) on issuance of common units by equity method investee					0	0	0	(41)	0	(41)	6,385
Operating income (loss)	73,339	(24,599)	25,269	23,457	37,928	25,947	25,391	32,324	97,466	121,590	129,153
Other expenses (income):
Interest expense									103,009	62,650	69,675
Loss on early extinguishment of debt									19,930	0	0
Foreign currency transaction loss (gain)									(4,709)	4,759	(1,067)
Loss (gain) on sale or impairment of non-operated equity method investment									0	30,644	(14,517)
Other expense (income), net									(1,226)	(994)	(1,284)
Total other expenses, net	39,579	31,753	12,033	33,639	9,809	18,684	9,944	58,622	117,004	97,059	52,807
Income (loss) from continuing operations before income taxes	33,760	(56,352)	13,236	(10,182)	28,119	7,263	15,447	(26,298)	(19,538)	24,531	76,346
Income tax expense (benefit)	31,141	(37,249)	3,625	95	16,119	11,898	4,658	(21,407)	(2,388)	11,268	33,530
Income (loss) from continuing operations					12,000	(4,635)	10,789	(4,891)	(17,150)	13,263	42,816
Income (loss) from discontinued operations, net of income taxes					0	3	(2)	(2)	0	(1)	(4)
Net income (loss)	$ 2,619	$ (19,103)	$ 9,611	$ (10,277)	12,000	(4,632)	10,787	(4,893)	(17,150)	13,262	42,812
Less: net income attributable to noncontrolling interests					0	225	1,922	9,020	0	11,167	12,492
Net income (loss) attributable to SemGroup					$ 12,000	$ (4,857)	$ 8,865	$ (13,913)	(17,150)	2,095	30,320
Other comprehensive income (loss):
Currency translation adjustments									20,411	(14,224)	(32,142)
Other, net of income taxes									(298)	(1,128)	721
Total other comprehensive income (loss)									20,113	(15,352)	(31,421)
Comprehensive income (loss)									2,963	(2,090)	11,391
Less: comprehensive income attributable to noncontrolling interests									0	11,167	12,492
Comprehensive income (loss) attributable to SemGroup									$ 2,963	$ (13,257)	$ (1,101)
Net income (loss) attributable to SemGroup per common share (Note 17):
Basic	$ 0.03	$ (0.25)	$ 0.15	$ (0.16)	$ 0.18	$ (0.09)	$ 0.20	$ (0.32)	$ (0.24)	$ 0.04	$ 0.69
Diluted	$ 0.03	$ (0.25)	$ 0.15	$ (0.16)	$ 0.18	$ (0.09)	$ 0.19	$ (0.32)	$ (0.24)	$ 0.04	$ 0.69