Long-Term Debt (Details) (USD $)	Sep. 30, 2013	Dec. 31, 2012
Debt Instrument [Line Items]
Senior Notes	$ 300,000,000	$ 0
Line of Credit Facility [Abstract]
Capital leases	69,000	86,000
Total long-term debt	540,069,000	206,086,000
less: current portion of long-term debt	26,000	24,000
Noncurrent portion of long-term debt	540,043,000	206,062,000
SemMexico [Member]
Line of Credit Facility [Abstract]
Borrowings	0	0
Corporate [Member]
Line of Credit Facility [Abstract]
Borrowings	155,000,000	201,500,000
Revolving Credit Facility [Member] | SemMexico [Member]
Line of Credit Facility [Abstract]
Borrowings	0
Revolving Credit Facility [Member] | Corporate [Member]
Line of Credit Facility [Abstract]
Borrowings	155,000,000
Rose Rock Midstream L P [Member]
Line of Credit Facility [Abstract]
Borrowings	85,000,000	4,500,000
Noncurrent portion of long-term debt	$ 85,043,000	$ 4,562,000