Quarterly report pursuant to Section 13 or 15(d)

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

v3.19.3
DERIVATIVE INSTRUMENTS (Net (Loss) Gain on Derivative Instruments) (Details) - USD ($)
$ in Thousands
 3 Months Ended 9 Months Ended
Sep. 30, 2019
Sep. 30, 2018
Sep. 30, 2019
Sep. 30, 2018
Derivative [Line Items]        
Net gain (loss) on natural gas, oil and NGLs derivatives $ 27,074 $ (9,663) $ 178,169 $ (96,737)
Natural gas derivatives        
Derivative [Line Items]        
Net gain (loss) on natural gas, oil and NGLs derivatives 11,731 14,101 147,774 (26,789)
Oil derivatives        
Derivative [Line Items]        
Net gain (loss) on natural gas, oil and NGLs derivatives 12,736 (11,610) 24,153 (45,176)
NGLs derivatives        
Derivative [Line Items]        
Net gain (loss) on natural gas, oil and NGLs derivatives 3,641 (12,154) 7,276 (24,772)
Contingent consideration arrangement        
Derivative [Line Items]        
Net gain (loss) on natural gas, oil and NGLs derivatives $ (1,034) $ 0 $ (1,034) $ 0