Derivatives and Fair Value (Effect of Derivative Instruments on the Condensed Consolidated Statements of Operations) (Details) - Crude Oil Swaps [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss)	$ (446)	$ 4,264	$ (1,032)
Realized Gain - Contract Settlements [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss)	2,439	744	195
Unrealized (Gain) Loss [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss)	$ (2,885)	$ 3,520	$ (1,227)