Condensed Consolidating Guarantor Financial Statements - Statements of Operations (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Revenues:
Product	$ 288,736	$ 402,986	$ 508,867	$ 830,016
Service	66,604	53,450	128,481	101,957
Other	21,886	25,788	38,188	49,134
Revenue	377,226	482,224	675,536	981,107
Expenses:
Cost of products sold	244,158	368,527	436,230	753,640
Operating	60,800	59,424	113,890	110,202
General and administrative	22,917	21,850	55,227	40,586
Depreciation and amortization	24,674	22,062	48,408	45,699
Loss (gain) on disposal of long-lived assets, net	1,372	19,315	2,430	19,257
Total expenses	353,921	491,178	656,185	969,384
Earnings from equity method investments	23,903	19,187	44,462	34,149
Gain on issuance of common units by equity method investee	5,897	0	5,897	8,127
Operating income	53,105	10,233	69,710	53,999
Other expenses (income), net:
Interest expense	16,822	10,360	31,413	19,587
Foreign currency transaction loss (gain)	(295)	167	(814)	(516)
Other income, net	(6,718)	18,962	(14,703)	17,915
Total other expenses, net	9,809	29,489	15,896	36,986
Income (loss) from continuing operations before income taxes	43,296	(19,256)	53,814	17,013
Income tax expense (benefit)	14,861	(6,672)	19,603	9,854
Income (loss) from continuing operations	28,435	(12,584)	34,211	7,159
Loss from discontinued operations, net of income taxes	(2)	0	(2)	(5)
Net income	28,433	(12,584)	34,209	7,154
Less: net income attributable to noncontrolling interests	5,136	5,025	9,446	11,250
Net income (loss) attributable to SemGroup	23,297	(17,609)	24,763	(4,096)
Other comprehensive income (loss), net of income taxes	5,520	6,685	(3,540)	3,713
Comprehensive income (loss)	33,953	(5,899)	30,669	10,867
Less: comprehensive income attributable to noncontrolling interests	5,136	5,025	9,446	11,250
Comprehensive income (loss) attributable to SemGroup	28,817	(10,924)	21,223	(383)
Parent Company [Member]
Revenues:
Product	0	0	0	0
Service	0	0	0	0
Other	0	0	0	0
Revenue	0	0	0	0
Expenses:
Cost of products sold	0	0	0	0
Operating	0	0	0	0
General and administrative	4,626	4,985	22,228	9,518
Depreciation and amortization	329	417	623	852
Loss (gain) on disposal of long-lived assets, net	0	5,945	0	5,945
Total expenses	4,955	11,347	22,851	16,315
Earnings from equity method investments	28,583	10,493	43,388	31,319
Gain on issuance of common units by equity method investee	5,897		5,897	8,127
Operating income	29,525	(854)	26,434	23,131
Other expenses (income), net:
Interest expense	781	3,093	2,203	5,583
Foreign currency transaction loss (gain)	(5)	0	(5)	0
Other income, net	(7,401)	18,099	(16,087)	16,301
Total other expenses, net	(6,625)	21,192	(13,889)	21,884
Income (loss) from continuing operations before income taxes	36,150	(22,046)	40,323	1,247
Income tax expense (benefit)	12,853	(4,437)	15,560	5,343
Income (loss) from continuing operations	23,297		24,763	(4,096)
Loss from discontinued operations, net of income taxes	0		0	0
Net income	23,297	(17,609)	24,763	(4,096)
Less: net income attributable to noncontrolling interests	0	0	0	0
Net income (loss) attributable to SemGroup	23,297	(17,609)	24,763	(4,096)
Other comprehensive income (loss), net of income taxes	(2,346)	(1,680)	6,300	(2,426)
Comprehensive income (loss)	20,951	(19,289)	31,063	(6,522)
Less: comprehensive income attributable to noncontrolling interests	0	0	0	0
Comprehensive income (loss) attributable to SemGroup	20,951	(19,289)	31,063	(6,522)
Guarantor Subsidiaries [Member]
Revenues:
Product	50,293	82,212	101,346	180,337
Service	15,743	9,593	30,202	10,812
Other	0	0	0	0
Revenue	66,036	91,805	131,548	191,149
Expenses:
Cost of products sold	35,632	67,306	76,300	144,840
Operating	8,822	8,041	16,936	15,096
General and administrative	2,642	2,250	4,706	4,301
Depreciation and amortization	7,255	7,114	14,288	11,930
Loss (gain) on disposal of long-lived assets, net	108	54,695	107	54,705
Total expenses	54,459	139,406	112,337	230,872
Earnings from equity method investments	15,048	49,289	27,576	59,779
Gain on issuance of common units by equity method investee	0		0	0
Operating income	26,625	1,688	46,787	20,056
Other expenses (income), net:
Interest expense	6,160	2,013	11,651	4,397
Foreign currency transaction loss (gain)	0	0	0	0
Other income, net	0	0	0	0
Total other expenses, net	6,160	2,013	11,651	4,397
Income (loss) from continuing operations before income taxes	20,465	(325)	35,136	15,659
Income tax expense (benefit)	0	0	0	0
Income (loss) from continuing operations	20,465		35,136	15,659
Loss from discontinued operations, net of income taxes	(1)		(1)	0
Net income	20,464	(325)	35,135	15,659
Less: net income attributable to noncontrolling interests	0	0	0	0
Net income (loss) attributable to SemGroup	20,464	(325)	35,135	15,659
Other comprehensive income (loss), net of income taxes	0	0	0	0
Comprehensive income (loss)	20,464	(325)	35,135	15,659
Less: comprehensive income attributable to noncontrolling interests	0	0	0	0
Comprehensive income (loss) attributable to SemGroup	20,464	(325)	35,135	15,659
Non-Guarantor Subsidiaries [Member]
Revenues:
Product	244,886	330,549	419,938	669,346
Service	50,861	43,857	98,279	91,145
Other	21,886	25,788	38,188	49,134
Revenue	317,633	400,194	556,405	809,625
Expenses:
Cost of products sold	214,969	310,996	372,347	628,467
Operating	51,978	51,383	96,954	95,106
General and administrative	15,649	14,615	28,293	26,767
Depreciation and amortization	17,090	14,531	33,497	32,917
Loss (gain) on disposal of long-lived assets, net	1,264	(41,325)	2,323	(41,393)
Total expenses	300,950	350,200	533,414	741,864
Earnings from equity method investments	17,683	10,136	38,547	17,832
Gain on issuance of common units by equity method investee	0		0	0
Operating income	34,366	60,130	61,538	85,593
Other expenses (income), net:
Interest expense	10,614	6,086	19,058	11,256
Foreign currency transaction loss (gain)	(290)	167	(809)	(516)
Other income, net	(50)	31	(115)	(35)
Total other expenses, net	10,274	6,284	18,134	10,705
Income (loss) from continuing operations before income taxes	24,092	53,846	43,404	74,888
Income tax expense (benefit)	2,008	(2,235)	4,043	4,511
Income (loss) from continuing operations	22,084		39,361	70,377
Loss from discontinued operations, net of income taxes	(1)		(1)	(5)
Net income	22,083	56,081	39,360	70,372
Less: net income attributable to noncontrolling interests	5,136	5,025	9,446	11,250
Net income (loss) attributable to SemGroup	16,947	51,056	29,914	59,122
Other comprehensive income (loss), net of income taxes	7,866	8,365	(9,840)	6,139
Comprehensive income (loss)	29,949	64,446	29,520	76,511
Less: comprehensive income attributable to noncontrolling interests	5,136	5,025	9,446	11,250
Comprehensive income (loss) attributable to SemGroup	24,813	59,421	20,074	65,261
Consolidation, Eliminations [Member]
Revenues:
Product	(6,443)	(9,775)	(12,417)	(19,667)
Service	0	0	0	0
Other	0	0	0	0
Revenue	(6,443)	(9,775)	(12,417)	(19,667)
Expenses:
Cost of products sold	(6,443)	(9,775)	(12,417)	(19,667)
Operating	0	0	0	0
General and administrative	0	0	0	0
Depreciation and amortization	0	0	0	0
Loss (gain) on disposal of long-lived assets, net	0	0	0	0
Total expenses	(6,443)	(9,775)	(12,417)	(19,667)
Earnings from equity method investments	(37,411)	(50,731)	(65,049)	(74,781)
Gain on issuance of common units by equity method investee	0		0	0
Operating income	(37,411)	(50,731)	(65,049)	(74,781)
Other expenses (income), net:
Interest expense	(733)	(832)	(1,499)	(1,649)
Foreign currency transaction loss (gain)	0	0	0	0
Other income, net	733	832	1,499	1,649
Total other expenses, net	0	0	0	0
Income (loss) from continuing operations before income taxes	(37,411)	(50,731)	(65,049)	(74,781)
Income tax expense (benefit)	0	0	0	0
Income (loss) from continuing operations	(37,411)		(65,049)	(74,781)
Loss from discontinued operations, net of income taxes	0		0	0
Net income	(37,411)	(50,731)	(65,049)	(74,781)
Less: net income attributable to noncontrolling interests	0	0	0	0
Net income (loss) attributable to SemGroup	(37,411)	(50,731)	(65,049)	(74,781)
Other comprehensive income (loss), net of income taxes	0	0	0	0
Comprehensive income (loss)	(37,411)	(50,731)	(65,049)	(74,781)
Less: comprehensive income attributable to noncontrolling interests	0	0	0	0
Comprehensive income (loss) attributable to SemGroup	$ (37,411)	$ (50,731)	$ (65,049)	$ (74,781)