Quarterly report pursuant to Section 13 or 15(d)

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

v3.4.0.3
Derivative Instruments and Hedging Activities (Schedule of Gain or Loss on Derivative Contracts) (Details) - USD ($)
$ in Thousands
 3 Months Ended
Mar. 31, 2016
Mar. 31, 2015
Derivative Instruments, Gain (Loss) [Line Items]    
Net gain (loss) on fair value adjustments $ (8,648) $ (7,914)
Total gain (loss) on derivative contracts (932) 2,429
Crude Oil [Member] | Not Designated as Hedging Instrument [Member]    
Derivative Instruments, Gain (Loss) [Line Items]    
Net gain on settlements 7,507 9,952
Net gain (loss) on fair value adjustments (9,137) (7,789)
Total gain (loss) on derivative contracts (1,630) 2,163
Natural Gas [Member] | Not Designated as Hedging Instrument [Member]    
Derivative Instruments, Gain (Loss) [Line Items]    
Net gain on settlements 209 391
Net gain (loss) on fair value adjustments 489 (125)
Total gain (loss) on derivative contracts $ 698 $ 266