Equity - Equity rollforward (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
SemGroup owners’ equity:
Balance at December 31, 2015	$ 1,196,356
Net income (loss)	(6,248)	$ 5,776
Other comprehensive loss, net of income taxes	(4,109)	$ (9,060)
Distributions to noncontrolling interests	(10,833)
Dividends paid	(19,887)
Unvested dividend equivalent rights	375
Non-cash equity compensation	2,831
Issuance of common stock under compensation plans	690
Repurchase of common stock	(807)
Balance at March 31, 2016	1,158,368
Common Stock [Member]
SemGroup owners’ equity:
Balance at December 31, 2015	439
Net income (loss)	0
Other comprehensive loss, net of income taxes	0
Distributions to noncontrolling interests	0
Dividends paid	0
Unvested dividend equivalent rights	0
Non-cash equity compensation	0
Issuance of common stock under compensation plans	2
Repurchase of common stock	0
Balance at March 31, 2016	441
Additional Paid-In Capital [Member]
SemGroup owners’ equity:
Balance at December 31, 2015	1,217,255
Net income (loss)	0
Other comprehensive loss, net of income taxes	0
Distributions to noncontrolling interests	0
Dividends paid	(19,887)
Unvested dividend equivalent rights	222
Non-cash equity compensation	2,466
Issuance of common stock under compensation plans	688
Repurchase of common stock	0
Balance at March 31, 2016	1,200,744
Treasury Stock [Member]
SemGroup owners’ equity:
Balance at December 31, 2015	(5,593)
Net income (loss)	0
Other comprehensive loss, net of income taxes	0
Distributions to noncontrolling interests	0
Dividends paid	0
Unvested dividend equivalent rights	0
Non-cash equity compensation	0
Issuance of common stock under compensation plans	0
Repurchase of common stock	(807)
Balance at March 31, 2016	(6,400)
Accumulated Deficit [Member]
SemGroup owners’ equity:
Balance at December 31, 2015	(38,012)
Net income (loss)	(15,268)
Other comprehensive loss, net of income taxes	0
Distributions to noncontrolling interests	0
Dividends paid	0
Unvested dividend equivalent rights	0
Non-cash equity compensation	0
Issuance of common stock under compensation plans	0
Repurchase of common stock	0
Balance at March 31, 2016	(53,280)
Accumulated Other Comprehensive Income (Loss) [Member]
SemGroup owners’ equity:
Balance at December 31, 2015	(58,562)
Net income (loss)	0
Other comprehensive loss, net of income taxes	(4,109)
Distributions to noncontrolling interests	0
Dividends paid	0
Unvested dividend equivalent rights	0
Non-cash equity compensation	0
Issuance of common stock under compensation plans	0
Repurchase of common stock	0
Balance at March 31, 2016	(62,671)
Noncontrolling Interest [Member]
SemGroup owners’ equity:
Balance at December 31, 2015	80,829
Net income (loss)	9,020
Other comprehensive loss, net of income taxes	0
Distributions to noncontrolling interests	(10,833)
Unvested dividend equivalent rights	153
Non-cash equity compensation	365
Issuance of common stock under compensation plans	0
Repurchase of common stock	0
Balance at March 31, 2016	$ 79,534