Quarterly report pursuant to Section 13 or 15(d)

Derivatives and Fair Value (Effect of Derivative Instruments on the Condensed Consolidated Statements of Operations) (Details)

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Derivatives and Fair Value (Effect of Derivative Instruments on the Condensed Consolidated Statements of Operations) (Details) - Crude Oil Swaps [Member] - USD ($)
$ in Thousands
 3 Months Ended 9 Months Ended
Sep. 30, 2021
Sep. 30, 2021
Sep. 30, 2020
Derivative Instruments, Gain (Loss) [Line Items]      
Derivative instruments gain (loss), net $ (5,147) $ (21,070) $ 6,583
Realized Gain (Loss) - Contract Settlements [Member]      
Derivative Instruments, Gain (Loss) [Line Items]      
Derivative instruments gain (loss), net (4,186) (10,189) 7,216
Unrealized Loss [Member]      
Derivative Instruments, Gain (Loss) [Line Items]      
Derivative instruments gain (loss), net $ (961) $ (10,881) $ (633)