Risk Management and Derivative Instruments - Unrealized and Realized Gains and Losses Related to Derivative Instruments (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Derivative Instruments Gain Loss [Line Items]
(Gain) loss on commodity derivative instruments	$ 14,352	$ (28,725)	$ (74,196)	$ (19,231)
Interest expense, net	(3,362)	(5,276)	(17,218)	(13,787)
Commodity derivatives [Member]
Derivative Instruments Gain Loss [Line Items]
(Gain) loss on commodity derivative instruments	14,352	(28,725)	(74,196)	(19,231)
Interest rate derivatives [Member]
Derivative Instruments Gain Loss [Line Items]
Interest expense, net	$ (20)	$ (199)	$ 4,034	$ 334