Equity - Equity rollforward (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
	Jun. 22, 2016	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
SemGroup owners’ equity:
Balance at December 31, 2015				$ 1,196,356
Net income (loss)		$ 9,931	$ 28,433	3,683	$ 34,209
Other comprehensive income (loss), net of income taxes		6,591	$ 5,520	2,482	$ (3,540)
Stock Issued During Period, Value, New Issues	$ 228,546			228,546
Distributions to noncontrolling interests				(21,485)
Dividends paid				(39,720)
Unvested dividend equivalent rights				272
Non-cash equity compensation				5,323
Issuance of common stock under compensation plans				775
Repurchase of common stock				(904)
Balance at June 30, 2016		1,375,328		1,375,328
Common Stock [Member]
SemGroup owners’ equity:
Balance at December 31, 2015				439
Net income (loss)				0
Other comprehensive income (loss), net of income taxes				0
Stock Issued During Period, Value, New Issues				86
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				1
Repurchase of common stock				0
Balance at June 30, 2016		526		526
Additional Paid-In Capital [Member]
SemGroup owners’ equity:
Balance at December 31, 2015				1,217,255
Net income (loss)				0
Other comprehensive income (loss), net of income taxes				0
Stock Issued During Period, Value, New Issues				228,460
Distributions to noncontrolling interests				0
Dividends paid				(39,720)
Unvested dividend equivalent rights				206
Non-cash equity compensation				4,592
Issuance of common stock under compensation plans				774
Repurchase of common stock				0
Balance at June 30, 2016		1,411,567		1,411,567
Treasury Stock [Member]
SemGroup owners’ equity:
Balance at December 31, 2015				(5,593)
Net income (loss)				0
Other comprehensive income (loss), net of income taxes				0
Stock Issued During Period, Value, New Issues				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				(904)
Balance at June 30, 2016		(6,497)		(6,497)
Accumulated Deficit [Member]
SemGroup owners’ equity:
Balance at December 31, 2015				(38,012)
Net income (loss)				(7,259)
Other comprehensive income (loss), net of income taxes				0
Stock Issued During Period, Value, New Issues				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 June 30, 2016		(45,271)		(45,271)
Accumulated Other Comprehensive Income (Loss) [Member]
SemGroup owners’ equity:
Balance at December 31, 2015				(58,562)
Net income (loss)				0
Other comprehensive income (loss), net of income taxes				2,482
Stock Issued During Period, Value, New Issues				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 June 30, 2016		(56,080)		(56,080)
Noncontrolling Interest [Member]
SemGroup owners’ equity:
Balance at December 31, 2015				80,829
Net income (loss)				10,942
Other comprehensive income (loss), net of income taxes				0
Stock Issued During Period, Value, New Issues				0
Distributions to noncontrolling interests				(21,485)
Unvested dividend equivalent rights				66
Non-cash equity compensation				731
Issuance of common stock under compensation plans				0
Repurchase of common stock				0
Balance at June 30, 2016		$ 71,083		$ 71,083