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, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss)	$ 1,911	$ (1,010)	$ (1)	$ (1,010)
Realized Gain - Contract Settlements [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss)	432	(11)	1,563	(11)
Unrealized Loss [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss)	$ 1,479	$ (999)	$ (1,564)	$ (999)