Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2021	Dec. 31, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset, Current	$ 13,093	$ 75,506
Derivative Asset, Noncurrent	5,269	25,449
Liabilities:
Commodity derivative liabilities – current	(44,328)	(85,106)
Derivative Liability, Noncurrent	(14,914)	(28,434)
Fair Value, Measurements, Recurring \| Commodity contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset, Current	13,093	75,506
Derivative Asset, Noncurrent	5,269	25,449
Liabilities:
Commodity derivative liabilities – current	(40,598)	81,451
Derivative Liability, Noncurrent	(14,299)	(26,789)
Fair Value, Measurements, Recurring \| Commodity contracts \| Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset, Current	0	0
Derivative Asset, Noncurrent	0	0
Liabilities:
Commodity derivative liabilities – current	0	0
Derivative Liability, Noncurrent	0	0
Fair Value, Measurements, Recurring \| Commodity contracts \| Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset, Current	13,093	75,506
Derivative Asset, Noncurrent	5,269	25,449
Liabilities:
Commodity derivative liabilities – current	(40,598)	81,451
Derivative Liability, Noncurrent	(14,299)	(26,789)
Fair Value, Measurements, Recurring \| Commodity contracts \| Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset, Current	0	0
Derivative Asset, Noncurrent	0	0
Liabilities:
Commodity derivative liabilities – current	0	0
Derivative Liability, Noncurrent	0	0
Fair Value, Measurements, Recurring \| Interest Rate Swap
Liabilities:
Commodity derivative liabilities – current	(3,730)
Derivative Liability, Noncurrent	(615)
Fair Value, Measurements, Recurring \| Interest Rate Swap \| Level 2
Liabilities:
Commodity derivative liabilities – current	(3,730)	(3,655)
Derivative Liability, Noncurrent	$ (615)	$ (1,645)
Crude Oil \| Commodity contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Third-party quoted forward prices	NYMEX WTI
MEH [Member] \| Commodity contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Third-party quoted forward prices	MEH
Natural Gas [Member] \| Commodity contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Third-party quoted forward prices	NYMEX HH
Natural Gas Liquids \| Commodity contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Third-party quoted forward prices	OPIS Mt Belv Ethane

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, expected to be settled within one year or normal operating cycle, if longer. Includes assets not subject to a master netting arrangement and not elected to be offset.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312

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Fair value, after the effects of master netting arrangements, of a financial liability or 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, expected to be settled after one year or the normal operating cycle, if longer. Includes assets not subject to a master netting arrangement and not elected to be offset.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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