v3.10.0.1
Derivative Instruments and Fair Value Measurements - Summary of Commodity Derivatives (Loss) Gain (Detail) - USD ($)
$ in Thousands
3 Months Ended 9 Months Ended
Sep. 30, 2018
Sep. 30, 2017
Sep. 30, 2018
Sep. 30, 2017
Derivatives Not Designated as Hedging Instruments [Member]        
Derivatives Fair Value [Line Items]        
Commodity derivative (loss) gain $ (3,256) $ (3,560) $ (10,068) $ 1,115
Derivatives Not Designated as Hedging Instruments [Member] | Net Cash (Payment) Receipt on Derivatives Settlements [Member]        
Derivatives Fair Value [Line Items]        
Commodity derivative (loss) gain (3,172) (523) (6,685) (1,481)
Derivatives Not Designated as Hedging Instruments [Member] | Non-Cash Fair Value (Loss) Gain on Derivatives [Member]        
Derivatives Fair Value [Line Items]        
Commodity derivative (loss) gain (84) $ (3,037) (3,383) $ 2,596
Derivatives Designated as Hedging [Member] | Cash Flow Hedges [Member] | Oil, NGLs and Gas Sales [Member]        
Derivatives Fair Value [Line Items]        
Commodity derivative (loss) gain $ (85)   $ (23)