Financial Instruments - Effect of Derivative Instruments on Consolidated Statements of Operations (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain/loss recognized in income	$ (4,148)	$ 1,235
Derivatives Not Designated as Cash-Flow Hedging Instruments [Member] | Natural Gas Commodity Contracts [Member] | Unrealized gain (loss) on derivative instruments, net
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain/loss recognized in income	123	(394)
Derivatives Not Designated as Cash-Flow Hedging Instruments [Member] | Natural Gas Commodity Contracts [Member] | Realized gain (loss) on derivative instruments, net
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain/loss recognized in income	90	(278)
Derivatives Not Designated as Cash-Flow Hedging Instruments [Member] | Crude Oil Commodity Contracts [Member] | Unrealized (loss) gain on derivative instruments, net
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain/loss recognized in income	(2,776)	5,600
Derivatives Not Designated as Cash-Flow Hedging Instruments [Member] | Crude Oil Commodity Contracts [Member] | Realized (loss) on derivative instruments, net
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain/loss recognized in income	(1,814)	(3,642)
Derivatives Not Designated as Cash-Flow Hedging Instruments [Member] | Natural Gas Liquid Contracts [Member] | Unrealized (loss) gain on derivative instruments, net
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain/loss recognized in income	(124)	124
Derivatives Not Designated as Cash-Flow Hedging Instruments [Member] | Natural Gas Liquid Contracts [Member] | Realized gain (loss) on derivative instruments, net
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain/loss recognized in income	$ 353	$ (175)