Long-Term Debt (Details Textual)	9 Months Ended							9 Months Ended	3 Months Ended	9 Months Ended						9 Months Ended	3 Months Ended	9 Months Ended					3 Months Ended	9 Months Ended			3 Months Ended					9 Months Ended						9 Months Ended
	Sep. 30, 2012 USD ($)	Sep. 30, 2012 MXN	Feb. 28, 2011 Agreement	Sep. 30, 2012 Letter of Credit [Member] USD ($)	Sep. 30, 2012 Letter of Credit [Member] MXN	Feb. 27, 2012 Letter of Credit [Member] USD ($)	Sep. 30, 2012 Eurodollar Rate Borrowings [Member] USD ($)	Sep. 30, 2012 Alternate Base Rate Borrowings [Member] USD ($)	Sep. 30, 2012 Revolving Credit Agreements [Member] USD ($)	Sep. 30, 2012 Revolving Credit Agreements [Member] USD ($)	Sep. 30, 2012 Revolving Credit Agreements [Member] MXN	Sep. 30, 2012 Extended Credit Agreement [Member] USD ($)	Sep. 30, 2012 Extended Credit Agreement [Member] MXN	Sep. 30, 2012 3.23% Eurodollar Rate Borrowings [Member] USD ($)	Sep. 30, 2012 2.97% Eurodollar Rate Borrowings [Member] USD ($)	Sep. 30, 2012 Minimum [Member]	Sep. 30, 2012 SemGroup Corporate Revolving Credit Facility [Member] USD ($)	Sep. 30, 2012 SemGroup Corporate Revolving Credit Facility [Member] USD ($)	Sep. 30, 2012 SemGroup Corporate Revolving Credit Facility [Member] Eurodollar Rate Borrowings [Member]	Sep. 30, 2012 SemGroup Corporate Revolving Credit Facility [Member] Minimum [Member] Eurodollar Rate Borrowings [Member]	Dec. 31, 2012 SemGroup Corporate Revolving Credit Facility [Member] Maximum [Member] USD ($)	Sep. 30, 2012 SemGroup Corporate Revolving Credit Facility [Member] Maximum [Member] USD ($)	Sep. 30, 2012 Rose Rock Credit Facility [Member] USD ($)	Sep. 30, 2012 Rose Rock Credit Facility [Member] USD ($)	Sep. 30, 2012 Rose Rock Credit Facility [Member] Minimum [Member]	Sep. 30, 2012 Rose Rock Credit Facility [Member] Maximum [Member]	Mar. 31, 2012 SemLogistics Credit Facility [Member] USD ($)	Sep. 30, 2012 SemLogistics Credit Facility [Member] GBP (£)	Dec. 31, 2011 SemLogistics Credit Facility [Member] USD ($)	Dec. 31, 2010 SemLogistics Credit Facility [Member] Revolving Credit Agreements [Member] GBP (£)	Dec. 31, 2010 SemLogistics Credit Facility [Member] Term Loan [Member] GBP (£)	Sep. 30, 2012 SemMexico Credit Facility [Member]	Sep. 30, 2011 SemMexico facilities [Member] MXN	Sep. 30, 2012 Letter of Credit [Member] SemGroup Corporate Revolving Credit Facility [Member] USD ($)	Sep. 30, 2012 Letter of Credit [Member] SemGroup Corporate Revolving Credit Facility [Member] Maximum [Member] USD ($)	Sep. 30, 2012 Revolving Credit Facility [Member] USD ($)	Aug. 31, 2012 Revolving Credit Facility [Member] USD ($)	Sep. 30, 2012 1.75% Letter of Credit [Member] Rose Rock Credit Facility, Bilateral Letters of Credit[Member] Revolving Credit Agreements [Member] USD ($)	Sep. 30, 2012 2.0% Letter of Credit [Member] Secured Bilateral [Member] Revolving Credit Facility [Member] USD ($)	Sep. 30, 2012 MEXICO
Long Term Debt (Textual) [Abstract]
Capacity of revolving credit facility														$ 50,000,000	$ 40,000,000						$ 320,000,000	$ 300,000,000	$ 150,000,000	$ 150,000,000						£ 15,000,000	£ 15,000,000
Borrowings outstanding	2,100,000	26,700,000			292,800,000		90,000,000				0						189,500,000	189,500,000																				2,700,000
Amount of Incurred Interest		0				8,400,000		99,500,000															38,200,000	38,200,000										2,100,000	250,000,000				5,700,000
Number of Interest Swap Agreements			3
LIBOR rate used to calculate effective interest rate	0.4606%	0.4606%																	0.7334%																			1.75%
Margin added to LIBOR for determining effective interest rate																			2.50%	2.50%
Prime rate used to determine interest rate								3.25%																								1.50%
Interest rate in effect	4.75%	4.75%					2.96%	3.23%															2.25%	2.25%															2.00%
Debt instrument, applicable margin percentage								1.50%
Fees charged on outstanding letters of credit effect rate																2.50%
Percentage of line of credit facility fronting fee	0.25%	0.25%																						0.25%
Commitment fee on unused capacity								0.50%																	0.375%	0.50%
Capitalized loan fees, net of accumulated amortization								3,700,000															1,600,000	1,600,000
Fees to lenders and advisors																													800,000
Swaps reclass from accumulated other comprehensive income to earnings																												300,000
Loss on terminations of interest rate swaps																											400,000
Maximum borrowing capacity									3,400,000	3,400,000	44,000,000	4,400,000	56,000,000																				80,000,000			400,000,000	200,000,000
Interest expense recorded									100,000	200,000							1,700,000	4,900,000					500,000	1,400,000
Bank prime rate									2.00%	2.00%		1.70%	1.70%																											4.80%
Effective interest rate	6.30%	6.30%
Amount of Line of Credit Exchange Rate				$ 22,800,000
Percentage of Fees charged on outstanding letters of credit on Specified Amount one	0.46%	0.46%