Annual report pursuant to Section 13 and 15(d)

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

v3.10.0.1
Derivative Instruments - Gain (Loss) on Derivative Instruments (Details) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Derivative [Line Items]      
Gain due to changes in fair value of derivative instruments $ (123,479) $ 213,679 $ (174,506)
Natural gas derivatives      
Derivative [Line Items]      
Gain due to changes in fair value of derivative instruments (116,130) 232,143 (165,933)
Oil derivatives      
Derivative [Line Items]      
Gain due to changes in fair value of derivative instruments (13,084) (3,350) (5,387)
Natural gas liquids derivatives      
Derivative [Line Items]      
Gain due to changes in fair value of derivative instruments $ 5,735 $ (15,114) $ (3,186)