Quarterly report pursuant to Section 13 or 15(d)

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

v3.5.0.2
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, 2016
Jun. 30, 2015
Jun. 30, 2016
Jun. 30, 2015
Derivative Instruments, Gain (Loss) [Line Items]        
Net loss on fair value adjustments     $ (28,149) $ (21,129)
Total loss on derivative contracts $ (15,484) $ (8,249) (16,416) (5,820)
Crude Oil [Member] | Not Designated as Hedging Instrument [Member]        
Derivative Instruments, Gain (Loss) [Line Items]        
Net gain on settlements 3,707 4,511 11,214 14,464
Net loss on fair value adjustments (18,466) (12,755) (27,604) (20,544)
Total loss on derivative contracts (14,759) (8,244) (16,390) (6,080)
Natural Gas [Member] | Not Designated as Hedging Instrument [Member]        
Derivative Instruments, Gain (Loss) [Line Items]        
Net gain on settlements 310 454 519 845
Net loss on fair value adjustments (1,035) (459) (545) (585)
Total loss on derivative contracts $ (725) $ (5) $ (26) $ 260