Quarterly report pursuant to Section 13 or 15(d)

Derivatives and Fair Value (Effect of Derivative Instruments on the Condensed Consolidated Statements of Operations) (Details)

v3.19.2
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)