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Debt - Wyoming Refining Credit Facilities (Details) - USD ($)
Dec. 21, 2017
Jul. 14, 2016
Revolving Credit Facility | Wyoming Refining Senior Secured Revolver    
Debt Instrument [Line Items]    
Line credit maximum borrowing amount   $ 30,000,000
Cost associated with termination of debt $ 100,000  
Term Loan | Wyoming Refining Senior Secured Term Loan    
Debt Instrument [Line Items]    
Periodic payment, principal amount   $ 2,300,000
Term Loan | Wyoming Refining Company | Wyoming Refining Senior Secured Term Loan | London Interbank Offered Rate (LIBOR)    
Debt Instrument [Line Items]    
Basis spread on variable rate   3.00%