Long-Term Debt (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Debt Instrument [Line Items]
Unamortized Debt Issuance Expense		$ (16,800)
Capital leases	$ 72	83
Total long-term debt	1,122,615	1,057,847
less: current portion of long-term debt	27	31
Long-term debt, net	1,122,588	1,057,816
Corporate, Non-Segment [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	300,000	300,000
Unamortized Debt Issuance Expense	(4,333)	(4,540)
Senior Notes	295,667	295,460
SemMexico [Member]
Debt Instrument [Line Items]
Borrowings	0	0
Revolving Credit Facility [Member] \| Corporate, Non-Segment [Member]
Debt Instrument [Line Items]
Borrowings	70,000	30,000
Rose Rock Midstream L P [Member]
Debt Instrument [Line Items]
Long-term debt, net	756,921	732,356
Rose Rock Midstream L P [Member] \| Rose Rock Notes due 2022 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	400,000	400,000
Unamortized Debt Issuance Expense	(6,709)	(6,975)
Senior Notes	393,291	393,025
Rose Rock Midstream L P [Member] \| Rose Rock Notes due 2023 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	350,000	350,000
Debt Instrument, Unamortized Discount	(5,317)	(5,455)
Unamortized Debt Issuance Expense	(5,098)	(5,266)
Senior Notes	339,585	339,279
Rose Rock Midstream L P [Member] \| Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Borrowings	$ 24,000	$ 0

Amount equal to the present value (the principal) at the beginning of the lease term of minimum lease payments during the lease term (excluding that portion of the payments representing executory costs such as insurance, maintenance, and taxes to be paid by the lessor, together with any profit thereon) net of payments or other amounts applied to the principal through the balance sheet date.

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Sum of the carrying values as of the balance sheet date of all debt, including all short-term borrowings, long-term debt, and capital lease obligations.

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Amount of long-term debt before deduction of unamortized discount or premium. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt, with initial maturities beyond one year or the normal operating cycle, if longer.

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The amount of debt discount that was originally recognized at the issuance of the instrument that has yet to be amortized.

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The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

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Amount of long-term debt and capital lease obligation due after one year or beyond the normal operating cycle, if longer.

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Including the current and noncurrent portions, carrying value as of the balance sheet date of Notes with the highest claim on the assets of the issuer in case of bankruptcy or liquidation (with maturities initially due after one year or beyond the operating cycle if longer). Senior note holders are paid off in full before any payments are made to junior note holders.

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The remaining balance of debt issuance expenses that were capitalized and are being amortized against income over the lives of the respective bond issues. This does not include the amounts capitalized as part of the cost of the utility plant or asset.

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