Risk Management and Hedging Activities - Schedule of Net Long or Short Positions Expected to be Realized (Detail)	9 Months Ended
	Sep. 30, 2020 MMBTU bbl	Sep. 30, 2019 MMBTU bbl
Crude Oil
Net (Short) Position, Volume [Abstract]
Net (Short) Position (Bbls), Year One | bbl	(253,000)	(549,000)
Net (Short) Position (Bbls), Year Two | bbl	(791,000)	(1,391,000)
Net (Short) Position (Bbls), Year Three | bbl	(43,000)	(154,000)
Net (Short) Position (Bbls), Year Four | bbl	0	0
Net Long (Short) Position (Bbls), Year Five | bbl	0	0
Net (Short) Positions (Bbls), Year Six | bbl	0
Natural Gas [Member]
Net Long (Short) Position, MMBtu [Abstract]
Net (Short) Long Position (MMBtu), Year One | MMBTU	(14,287,500)	(21,679,350)
Net (Short) Long Position (MMBtu), Year Two | MMBTU	(65,332,500)	(5,145,900)
Net Long Position (MMBtu), Year Three | MMBTU	(21,900,000)	0
Net Long Position (MMBtu), Year Four | MMBTU	0	0
Net Long Position (MMBtu), Year Five | MMBTU	0	0
Net Long (Short) Positions (MMBtu), year Six | MMBTU	0
Natural Gas Liquids
Net (Short) Position, Volume [Abstract]
Net (Short) Position (Bbls), Year One | bbl	(932,160)	(13,139,076)
Net (Short) Position (Bbls), Year Two | bbl	(8,471,590)	(17,677,943)
Net (Short) Position (Bbls), Year Three | bbl	(1,486,842)	(5,381,993)
Net (Short) Position (Bbls), Year Four | bbl	(1,440,000)	(1,140)
Net Long (Short) Position (Bbls), Year Five | bbl	(1,440,000)	0
Net (Short) Positions (Bbls), Year Six | bbl	(960,000)
Natural Gas Basis Swaps
Net Long (Short) Position, MMBtu [Abstract]
Net (Short) Long Position (MMBtu), Year One | MMBTU	5,600,000	2,135,000
Net (Short) Long Position (MMBtu), Year Two | MMBTU	(735,000)	18,507,500
Net Long Position (MMBtu), Year Three | MMBTU	12,775,000	3,650,000
Net Long Position (MMBtu), Year Four | MMBTU	7,300,000	8,212,500
Net Long Position (MMBtu), Year Five | MMBTU	7,630,000	7,300,000
Net Long (Short) Positions (MMBtu), year Six | MMBTU	1,365,000