Quarterly report pursuant to Section 13 or 15(d)

Derivative Instruments (Net Gain (Loss) on Derivative Instruments) (Details)

v3.7.0.1
Derivative Instruments (Net Gain (Loss) on Derivative Instruments) (Details) - USD ($)
$ in Thousands
 3 Months Ended 6 Months Ended
Jun. 30, 2017
Jun. 30, 2016
Jun. 30, 2017
Jun. 30, 2016
Derivative [Line Items]        
Net gain (loss) on natural gas, oil, and NGL derivatives $ 64,871 $ (137,392) $ 164,448 $ (79,657)
Natural gas derivatives        
Derivative [Line Items]        
Net gain (loss) on natural gas, oil, and NGL derivatives 56,668 (133,621) 142,945 (76,621)
Oil derivatives        
Derivative [Line Items]        
Net gain (loss) on natural gas, oil, and NGL derivatives 8,143 (2,628) 19,048 (1,346)
Natural gas liquids derivatives        
Derivative [Line Items]        
Net gain (loss) on natural gas, oil, and NGL derivatives $ 60 $ (1,143) $ 2,455 $ (1,690)