Equity (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013		Jun. 30, 2012
SemGroup owners' equity:
Beginning Balance			$ 1,021,528
Net income (loss) attributable to SemGroup	7,512	7,243	56,078		9,353
Other comprehensive income (loss), net of income taxes	(5,354)	(9,897)	(10,412)		2,858
Distributions to noncontrolling interests			(7,496)
Noncontrolling interest, increase from equity issuance			57,751
Sale of interest in equity investment to related party			(33,716)	[1]
Stock issued during period from warrant exercises			23,464
Dividends			(7,939)
Dividends, Share-based Compensation, Cash			(41)
Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition			3,259
Issuance of common stock under compensation plans			0
Repurchase of common stock			(371)
Ending Balance	1,102,105		1,102,105
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			23,460
Dividends			(7,939)
Dividends, Share-based Compensation, Cash			(25)
Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition			2,904
Issuance of common stock under compensation plans			(1)
Repurchase of common stock			0
Ending Balance	1,114,388		1,114,388
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			47,013
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	(98,661)		(98,661)
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			(10,412)
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	(11,711)		(11,711)
Noncontrolling Interest [Member]
SemGroup owners' equity:
Beginning Balance			129,134
Net income (loss) attributable to SemGroup			9,065
Other comprehensive income (loss), net of income taxes			0
Distributions to noncontrolling interests			(7,496)
Noncontrolling interest, increase from equity issuance			57,751
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			(16)
Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition			355
Issuance of common stock under compensation plans			0
Repurchase of common stock			0
Ending Balance	$ 98,277		$ 98,277

[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.