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