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
Mar. 31, 2017
Mar. 31, 2016
Derivative [Line Items]    
Net gain on gas, oil, and NGL derivatives $ 99,577 $ 57,735
Natural gas derivatives    
Derivative [Line Items]    
Net gain on gas, oil, and NGL derivatives 86,277 57,000
Oil derivatives    
Derivative [Line Items]    
Net gain on gas, oil, and NGL derivatives 10,905 1,282
Natural gas liquids derivatives    
Derivative [Line Items]    
Net gain on gas, oil, and NGL derivatives $ 2,395 $ (547)