Fair Value of Derivative Instruments on Condensed Consolidated Balance Sheets (Detail) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Derivatives, Fair Value [Line Items]
Derivative Asset, Current	$ 50,414	$ 4,131
Derivative liabilities	22,861	23,450
Derivative Asset, Noncurrent	2,619	2,750
Derivative Liability, Noncurrent	5,542	3,385
Derivative Liability	28,403	26,835
Derivative Asset	53,033	6,881
Commodity contracts
Derivatives, Fair Value [Line Items]
Derivative Asset	30,900
Commodity contracts \| Current Derivative Contract [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Current	50,414	4,131
Derivative liabilities	19,260	23,450
Commodity contracts \| Noncurrent Derivative Contract [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Noncurrent	2,619	2,750
Derivative Liability, Noncurrent	2,903	3,385
Interest Rate Swap
Derivatives, Fair Value [Line Items]
Derivative Liability	6,200
Interest Rate Swap \| Current Derivative Contract [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Current	0	0
Derivative liabilities	3,601	0
Interest Rate Swap \| Noncurrent Derivative Contract [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Noncurrent	0	0
Derivative Liability, Noncurrent	2,639	0
Fair Value, Measurements, Recurring \| Commodity contracts
Derivatives, Fair Value [Line Items]
Derivative Asset, Current	50,414	4,131
Derivative liabilities	19,260	(23,450)
Derivative Asset, Noncurrent	2,619	2,750
Derivative Liability, Noncurrent	2,903	$ 3,385
Fair Value, Measurements, Recurring \| Interest Rate Swap
Derivatives, Fair Value [Line Items]
Derivative Asset, Current	0
Derivative liabilities	3,601
Derivative Asset, Noncurrent	0
Derivative Liability, Noncurrent	$ 2,639

Fair value, after the effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets not subject to a master netting arrangement and not elected to be offset.

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