Quarterly report pursuant to Section 13 or 15(d)

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

v3.5.0.2
Derivative Instruments (Net Gain (Loss) On Derivative Instruments) (Details) - USD ($)
$ in Thousands
 3 Months Ended 9 Months Ended
Sep. 30, 2016
Sep. 30, 2015
Sep. 30, 2016
Sep. 30, 2015
Derivative [Line Items]        
Net gain (loss) on derivative instruments $ 35,281 $ 91,756 $ (44,376) $ 131,778
Gas sales        
Derivative [Line Items]        
Net gain (loss) on derivative instruments 33,167 79,684 (43,454) 118,137
Oil and condensate sales        
Derivative [Line Items]        
Net gain (loss) on derivative instruments 1,708 12,072 362 13,641
Natural gas liquids sales        
Derivative [Line Items]        
Net gain (loss) on derivative instruments $ 406 $ 0 $ (1,284) $ 0