Risk Management and Derivative Instruments - Unrealized and Realized Gains and Losses Related to Derivative Instruments (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Derivative Instruments Gain Loss [Line Items]
(Gain) loss on commodity derivative instruments	$ 63,898	$ 19,165	$ 98,486	$ (88,548)
Interest expense, net	(3,137)	(6,209)	(6,249)	(13,856)
Commodity derivatives [Member]
Derivative Instruments Gain Loss [Line Items]
(Gain) loss on commodity derivative instruments	63,898	19,165	98,486	(88,548)
Interest Rate Swaps [Member]
Derivative Instruments Gain Loss [Line Items]
Interest expense, net	$ 18	$ 438	$ (44)	$ 4,054