Quarterly report pursuant to Section 13 or 15(d)

Risk Management and Derivative Instruments - Gain Loss (Details)

v3.10.0.1
Risk Management and Derivative Instruments - Gain Loss (Details) - USD ($)
$ in Thousands
3 Months Ended 9 Months Ended
Sep. 30, 2018
Sep. 30, 2017
Sep. 30, 2018
Sep. 30, 2017
Gains (losses) on Commodity Derivative Contracts        
Net cash received (paid) for commodity derivative contracts not designated as hedging instruments     $ (7,532) $ 6,149
Gains (losses) on commodity derivative contracts - net $ (6,583) $ (3,591) (21,870) 8,767
Not designated as Hedging Instrument        
Gains (losses) on Commodity Derivative Contracts        
Net cash received (paid) for commodity derivative contracts not designated as hedging instruments 3,854 (2,909) 7,532 (6,149)
Unrealized net gains (losses) (2,729) (6,500) (14,338) 2,618
Gains (losses) on commodity derivative contracts - net $ (6,583) $ (3,591) $ (21,870) $ 8,767