Quarterly report pursuant to Section 13 or 15(d)

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

v3.19.3
Derivative Instruments and Hedging Activities (Schedule of Gain or Loss on Derivative Contracts) (Details) - USD ($)
$ in Thousands
 3 Months Ended 9 Months Ended
Sep. 30, 2019
Sep. 30, 2018
Sep. 30, 2019
Sep. 30, 2018
Derivative Instruments, Gain (Loss) [Line Items]        
Net gain (loss) on fair value adjustments     $ (30,979) $ (29,696)
Total gain (loss) on derivatives $ 21,809 $ (34,339) (31,415) (55,374)
Not Designated as Hedging Instrument        
Derivative Instruments, Gain (Loss) [Line Items]        
Total gain (loss) on derivatives 21,809 (34,339) (31,415) (55,374)
Not Designated as Hedging Instrument | Commodity - Oil        
Derivative Instruments, Gain (Loss) [Line Items]        
Net gain (loss) on settlements (1,045) (9,306) (7,048) (26,353)
Net gain (loss) on fair value adjustments 25,767 (24,476) (27,750) (28,720)
Total gain (loss) on derivatives 24,722 (33,782) (34,798) (55,073)
Not Designated as Hedging Instrument | Commodity - Natural gas        
Derivative Instruments, Gain (Loss) [Line Items]        
Net gain (loss) on settlements 2,056 67 6,612 675
Net gain (loss) on fair value adjustments (733) (624) (2,306) (976)
Total gain (loss) on derivatives 1,323 (557) 4,306 (301)
Credit Risk Contract | Not Designated as Hedging Instrument        
Derivative Instruments, Gain (Loss) [Line Items]        
Net gain (loss) on fair value adjustments $ (4,236) $ 0 $ (923) $ 0