Derivative Instruments - Financial Instruments for Hedging Volume (Detail)	Sep. 30, 2020 $ / unit bbl
Derivative, Swap Type | Oil (Bbls) | October – December 2020
Derivative Instruments, Gain (Loss) [Line Items]
Hedge backed oil volume | bbl	1,311,000
Weighted Average Price (usd per unit) | $ / unit	56.29
Derivative, Swap Type | Oil (Bbls) | For the year 2021
Derivative Instruments, Gain (Loss) [Line Items]
Hedge backed oil volume | bbl	3,098,000
Weighted Average Price (usd per unit) | $ / unit	54.30
Derivative, Swap Type | Oil (Bbls) | For the year 2022
Derivative Instruments, Gain (Loss) [Line Items]
Hedge backed oil volume | bbl	0
Weighted Average Price (usd per unit) | $ / unit	0
Derivative, Swap Type | Natural Gas (MMbtu) | October – December 2020
Derivative Instruments, Gain (Loss) [Line Items]
Weighted Average Price (usd per unit) | $ / unit	1.83
Hedge Backed Gas Volume | bbl	1,840,000
Derivative, Swap Type | Natural Gas (MMbtu) | For the year 2021
Derivative Instruments, Gain (Loss) [Line Items]
Weighted Average Price (usd per unit) | $ / unit	2.13
Hedge Backed Gas Volume | bbl	5,790,000
Derivative, Swap Type | Natural Gas (MMbtu) | For the year 2022
Derivative Instruments, Gain (Loss) [Line Items]
Weighted Average Price (usd per unit) | $ / unit	2.13
Hedge Backed Gas Volume | bbl	3,650,000
Derivative, Roll Swaps | Oil (Bbls) | October – December 2020
Derivative Instruments, Gain (Loss) [Line Items]
Hedge backed oil volume | bbl	138,000
Weighted Average Price (usd per unit) | $ / unit	(1.47)
Derivative, Roll Swaps | Oil (Bbls) | For the year 2021
Derivative Instruments, Gain (Loss) [Line Items]
Hedge backed oil volume | bbl	182,500
Weighted Average Price (usd per unit) | $ / unit	(0.25)
Derivative, Roll Swaps | Oil (Bbls) | For the year 2022
Derivative Instruments, Gain (Loss) [Line Items]
Hedge backed oil volume | bbl	0
Weighted Average Price (usd per unit) | $ / unit	0
Swaption | Oil (Bbls) | October – December 2020
Derivative Instruments, Gain (Loss) [Line Items]
Hedge backed oil volume | bbl	0
Weighted Average Price (usd per unit) | $ / unit	0
Swaption | Oil (Bbls) | For the year 2021
Derivative Instruments, Gain (Loss) [Line Items]
Hedge backed oil volume | bbl	0
Weighted Average Price (usd per unit) | $ / unit	0
Swaption | Oil (Bbls) | For the year 2022
Derivative Instruments, Gain (Loss) [Line Items]
Hedge backed oil volume | bbl	1,092,000
Weighted Average Price (usd per unit) | $ / unit	55.08