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Prepaid and Other Current Assets (Details) - USD ($)
$ in Thousands
Mar. 31, 2018
Dec. 31, 2017
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]    
Advances to suppliers for crude oil purchases $ 76,410 $ 0
Collateral posted with broker for derivative instruments 11 215
Prepaid insurance 5,306 7,547
Derivative assets 7,432 4,296
Other 8,978 5,221
Total $ 98,137 $ 17,279