Quarterly report pursuant to Section 13 or 15(d)

Derivative Instruments and Hedging Activities (Schedule of Gain or Loss on Derivative Contracts) (Details)

v3.19.2
Derivative Instruments and Hedging Activities (Schedule of Gain or Loss on Derivative Contracts) (Details) - 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]        
Net gain (loss) on fair value adjustments     $ (51,777) $ (4,594)
Total gain (loss) on derivatives $ 14,036 $ (16,554) (53,224) (21,036)
Not Designated as Hedging Instrument        
Derivative Instruments, Gain (Loss) [Line Items]        
Total gain (loss) on derivatives 14,036 (16,554) (53,224) (21,036)
Not Designated as Hedging Instrument | Commodity - Oil        
Derivative Instruments, Gain (Loss) [Line Items]        
Net gain (loss) on settlements (4,461) (8,131) (6,003) (17,049)
Net gain (loss) on fair value adjustments 13,310 (8,311) (53,517) (4,243)
Total gain (loss) on derivatives 8,849 (16,442) (59,520) (21,292)
Not Designated as Hedging Instrument | Commodity - Natural gas        
Derivative Instruments, Gain (Loss) [Line Items]        
Net gain (loss) on settlements 3,304 151 4,556 607
Net gain (loss) on fair value adjustments (1,430) (263) (1,573) (351)
Total gain (loss) on derivatives 1,874 (112) 2,983 256
Credit Risk Contract | Not Designated as Hedging Instrument        
Derivative Instruments, Gain (Loss) [Line Items]        
Net gain (loss) on fair value adjustments $ 3,313 $ 0 $ 3,313 $ 0