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		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Derivative Instruments, Gain (Loss) [Line Items]
Derivative instruments gain (loss), net	$ (9,969)	$ (756)	$ (15,923)	$ 6,583
Realized Gain (Loss) - Contract Settlements [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative instruments gain (loss), net	(4,293)	6,498	(6,003)	7,216
Unrealized Loss [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative instruments gain (loss), net	$ (5,676)	$ (7,254)	$ (9,920)	$ (633)