Long-Term Debt (Details Textual)	9 Months Ended			3 Months Ended	9 Months Ended							9 Months Ended		1 Months Ended	3 Months Ended		9 Months Ended									9 Months Ended				0 Months Ended				3 Months Ended	0 Months Ended	3 Months Ended		9 Months Ended					9 Months Ended
	Sep. 30, 2013 USD ($)	Sep. 30, 2012 USD ($)	Dec. 31, 2012 USD ($)	Sep. 30, 2013 Senior Notes [Member] USD ($)	Sep. 30, 2013 Senior Notes [Member] USD ($)	Sep. 30, 2013 sale of stock [Member]	Sep. 30, 2013 Registration Payment Arrangement, Arrangement [Domain]	Sep. 30, 2013 Registration Payment Arrangement, Arrangement [Domain] Minimum [Member]	Sep. 30, 2013 Registration Payment Arrangement, Arrangement [Domain] Maximum [Member]	Sep. 30, 2013 Corporate [Member] USD ($)	Dec. 31, 2012 Corporate [Member] USD ($)	Sep. 30, 2013 Corporate [Member] Letter of Credit [Member] USD ($)	Sep. 30, 2013 Corporate [Member] Letter of Credit [Member] Maximum [Member] USD ($)	May 31, 2013 Corporate [Member] Revolving Credit Facility [Member] USD ($)	Sep. 30, 2013 Corporate [Member] Revolving Credit Facility [Member] USD ($)	Sep. 30, 2012 Corporate [Member] Revolving Credit Facility [Member] USD ($)	Sep. 30, 2013 Corporate [Member] Revolving Credit Facility [Member] USD ($)	Sep. 30, 2012 Corporate [Member] Revolving Credit Facility [Member] USD ($)	May 03, 2013 Corporate [Member] Revolving Credit Facility [Member] USD ($)	Apr. 22, 2013 Corporate [Member] Revolving Credit Facility [Member] USD ($)	Sep. 30, 2013 Corporate [Member] Revolving Credit Facility [Member] Maximum [Member] USD ($)	Sep. 30, 2013 SemMexico [Member] USD ($)	Dec. 31, 2012 SemMexico [Member] USD ($)	Sep. 30, 2013 SemMexico [Member] Letter of Credit [Member] USD ($)	Sep. 30, 2013 SemMexico [Member] Letter of Credit [Member] MXN	Sep. 30, 2013 SemMexico [Member] Revolving Credit Facility [Member] USD ($)	Sep. 30, 2013 SemMexico [Member] Revolving Credit Facility [Member] MXN	Sep. 30, 2013 SemMexico [Member] Revolving Credit Agreements [Member] Additional Credit Agreement [Member] USD ($)	Sep. 30, 2013 SemMexico [Member] Revolving Credit Agreements [Member] Additional Credit Agreement [Member] MXN	Jan. 11, 2013 Rose Rock Midstream L P [Member] USD ($)	Sep. 30, 2013 Rose Rock Midstream L P [Member] USD ($)	Dec. 31, 2012 Rose Rock Midstream L P [Member] USD ($)	Sep. 30, 2013 Rose Rock Midstream L P [Member] Bilateral Letter of Credit [Member] USD ($)	Sep. 30, 2013 Rose Rock Midstream L P [Member] Letter of Credit [Member] USD ($)	Jan. 11, 2013 Rose Rock Midstream L P [Member] Revolving Credit Facility [Member] USD ($)	Sep. 30, 2013 Rose Rock Midstream L P [Member] Revolving Credit Facility [Member] USD ($)	Sep. 30, 2012 Rose Rock Midstream L P [Member] Revolving Credit Facility [Member] USD ($)	Sep. 30, 2013 Rose Rock Midstream L P [Member] Revolving Credit Facility [Member] USD ($)	Sep. 30, 2012 Rose Rock Midstream L P [Member] Revolving Credit Facility [Member] USD ($)	Jan. 13, 2013 Rose Rock Midstream L P [Member] Revolving Credit Facility [Member] USD ($)	Sep. 30, 2013 Rose Rock Midstream L P [Member] Revolving Credit Facility [Member] Eurodollar Rate Borrowings [Member] USD ($)	Sep. 30, 2013 Rose Rock Midstream L P [Member] Revolving Credit Facility [Member] Alternate Base Rate Borrowings [Member] USD ($)	Sep. 30, 2013 Rose Rock Midstream L P [Member] Revolving Credit Facility [Member] Minimum [Member]	Sep. 30, 2013 Rose Rock Midstream L P [Member] Revolving Credit Facility [Member] Maximum [Member]	Sep. 30, 2013 Rose Rock Midstream L P [Member] 1.75% Letter of Credit [Member] Bilateral Letter of Credit [Member] USD ($)	Sep. 30, 2013 Rose Rock Midstream L P [Member] 2.0% Letter of Credit [Member] Bilateral Letter of Credit [Member] USD ($)	Sep. 30, 2013 Rose Rock Midstream L P [Member] Debt issuance [Member] Subordinated Debt [Member] USD ($)	Sep. 30, 2013 Semcrude Pipeline [Member]
Debt Instrument [Line Items]
Senior Notes	$ 300,000,000		$ 0
Debt Instrument, Interest Rate, Stated Percentage				7.50%	7.50%
Proceeds from Issuance of Senior Long-term Debt	294,000,000
Senior Notes Redemable Prior to June 15, 2016	35.00%
Early Redemption Premium on Senior Notes Redeemed Prior to June 15, 2016	1.00%					107.50%
Basis point adjustment to discount rate	50
Redemption premium on senior notes in the event of a change in control	101.00%
Interest rate increase							0.25%	0.25%	1.00%
Interest expense recorded				6,000,000	7,100,000										2,300,000	1,700,000	5,000,000	4,900,000																		1,900,000	500,000	6,100,000	1,400,000
Unamortized debt costs				6,400,000	6,400,000										4,800,000		4,800,000																			3,700,000		3,700,000
Maximum borrowing capacity													250,000,000		500,000,000		500,000,000				500,000,000					3,300,000	44,000,000	4,300,000	56,000,000											385,000,000
Borrowings outstanding										155,000,000	201,500,000				155,000,000		155,000,000					0	0			0			0		85,000,000	4,500,000									30,000,000	55,000,000
Letters of credit outstanding												4,500,000												22,300,000	292,800,000								7,600,000	31,800,000											600,000	7,000,000
Interest rate in effect												3.25%			5.50%		5.50%							0.50%	0.50%									2.25%							2.53%	4.50%			1.75%	2.00%
Percentage of line of credit facility fronting fee												0.25%																						0.25%
Commitment fee on unused capacity																	0.50%																										0.375%	0.50%
Line of Credit Facility, Maximum Borrowing Incremental Increases																				300,000,000	100,000,000															200,000,000		200,000,000
Senior Unsecured Indebtedness Threshold																				200,000,000
Line of Credit Facility, Incremental Increase																			200,000,000
Proceeds from Lines of Credit																														133,500,000					133,500,000
Equity Method Investment, Ownership Percentage																																																33.00%
Debt Issuance Cost														2,200,000																								1,600,000
Minimum aggregate issuance to elect alternative financial covenants																																															200,000,000
Margin added to Prime Rate to determine effective interest rate																										2.00%	2.00%	1.70%	1.70%
Interest Costs Capitalized	2,900,000	200,000
Long-term Debt, Fair Value	$ 306,000,000