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, 2020	Mar. 31, 2019
Derivative Instruments, Gain (Loss) [Line Items]
Derivative instruments gain (loss), net	$ 7,339	$ (1,912)
Realized Gain - Contract Settlements [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative instruments gain (loss), net	718	1,131
Unrealized (Gain) Loss [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative instruments gain (loss), net	$ 6,621	$ (3,043)