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
	Mar. 31, 2021	Mar. 31, 2020
Derivative Instruments, Gain (Loss) [Line Items]
Derivative instruments gain (loss), net	$ (5,954)	$ 7,339
Realized Gain (Loss) - Contract Settlements [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative instruments gain (loss), net	(1,710)	718
Unrealized Gain (Loss) [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative instruments gain (loss), net	$ (4,244)	$ 6,621