Equity (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013		Sep. 30, 2012
SemGroup owners' equity:
Beginning Balance			$ 1,021,528
Net income (loss) attributable to SemGroup	3,135	(432)	59,213		8,921
Other comprehensive income (loss), net of income taxes	6,105	12,072	(4,307)		14,930
Distributions to noncontrolling interests			(11,458)
Noncontrolling interest, increase from equity issuance			210,226
Sale of interest in equity investment to related party			(33,716)	[1]
Stock issued during period from warrant exercises			23,758
Dividends			(16,387)
Dividends, Share-based Compensation, Cash			(80)
Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition			5,311
Issuance of common stock under compensation plans			0
Repurchase of common stock			(371)
Ending Balance	1,253,717		1,253,717
Common Stock [Member]
SemGroup owners' equity:
Beginning Balance			420
Net income (loss) attributable to SemGroup			0
Other comprehensive income (loss), net of income taxes			0
Distributions to noncontrolling interests			0
Noncontrolling interest, increase from equity issuance			0
Sale of interest in equity investment to related party			0	[1]
Stock issued during period from warrant exercises			4
Dividends			0
Dividends, Share-based Compensation, Cash			0
Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition			0
Issuance of common stock under compensation plans			1
Repurchase of common stock			0
Ending Balance	425		425
Additional Paid-In Capital [Member]
SemGroup owners' equity:
Beginning Balance			1,039,189
Net income (loss) attributable to SemGroup			0
Other comprehensive income (loss), net of income taxes			0
Distributions to noncontrolling interests			0
Noncontrolling interest, increase from equity issuance			0
Sale of interest in equity investment to related party			56,800	[1]
Stock issued during period from warrant exercises			23,754
Dividends			(16,387)
Dividends, Share-based Compensation, Cash			(47)
Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition			4,733
Issuance of common stock under compensation plans			(1)
Repurchase of common stock			0
Ending Balance	1,108,041		1,108,041
Treasury Stock [Member]
SemGroup owners' equity:
Beginning Balance			(242)
Net income (loss) attributable to SemGroup			0
Other comprehensive income (loss), net of income taxes			0
Distributions to noncontrolling interests			0
Noncontrolling interest, increase from equity issuance			0
Sale of interest in equity investment to related party			0	[1]
Stock issued during period from warrant exercises			0
Dividends			0
Dividends, Share-based Compensation, Cash			0
Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition			0
Issuance of common stock under compensation plans			0
Repurchase of common stock			(371)
Ending Balance	(613)		(613)
Accumulated Deficit [Member]
SemGroup owners' equity:
Beginning Balance			(145,674)
Net income (loss) attributable to SemGroup			44,784
Other comprehensive income (loss), net of income taxes			0
Distributions to noncontrolling interests			0
Noncontrolling interest, increase from equity issuance			0
Sale of interest in equity investment to related party			0	[1]
Stock issued during period from warrant exercises			0
Dividends			0
Dividends, Share-based Compensation, Cash			0
Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition			0
Issuance of common stock under compensation plans			0
Repurchase of common stock			0
Ending Balance	(100,890)		(100,890)
Accumulated Other Comprehensive Income (Loss) [Member]
SemGroup owners' equity:
Beginning Balance			(1,299)
Net income (loss) attributable to SemGroup			0
Other comprehensive income (loss), net of income taxes			(4,307)
Distributions to noncontrolling interests			0
Noncontrolling interest, increase from equity issuance			0
Sale of interest in equity investment to related party			0	[1]
Stock issued during period from warrant exercises			0
Dividends			0
Dividends, Share-based Compensation, Cash			0
Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition			0
Issuance of common stock under compensation plans			0
Repurchase of common stock			0
Ending Balance	(5,606)		(5,606)
Noncontrolling Interest [Member]
SemGroup owners' equity:
Beginning Balance			129,134
Net income (loss) attributable to SemGroup			14,429
Other comprehensive income (loss), net of income taxes			0
Distributions to noncontrolling interests			(11,458)
Noncontrolling interest, increase from equity issuance			210,226
Sale of interest in equity investment to related party			(90,516)	[1]
Stock issued during period from warrant exercises			0
Dividends			0
Dividends, Share-based Compensation, Cash			(33)
Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition			578
Issuance of common stock under compensation plans			0
Repurchase of common stock			0
Ending Balance	$ 252,360		$ 252,360

[1] * On January 13, 2013, we contributed a 33% interest in SemCrude Pipeline, L.L.C. to our consolidated subsidiary, Rose Rock. As this transaction was between entities under common control, the interest in SemCrude Pipeline, L.L.C. was recorded by Rose Rock based on SemGroup's book value. This amount represents the purchase price in excess of book value which was attributed to the noncontrolling interest owners of Rose Rock. The entry to additional paid-in capital has been recorded net of tax.