Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset, Current	$ 4,909	$ 75,506
Derivative Asset, Noncurrent	2,152	25,449
Liabilities:
Commodity derivative liabilities – current	(63,089)	(85,106)
Derivative Liability, Noncurrent	(21,416)	(28,434)
Long-term Debt, Fair Value	$ 762,000
Senior Notes, Interest Rate	925.00%
Fair Value, Measurements, Recurring | Commodity contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset, Current	$ 4,909	75,506
Derivative Asset, Noncurrent	2,152	25,449
Liabilities:
Commodity derivative liabilities – current	(60,593)	81,451
Derivative Liability, Noncurrent	(21,416)	(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	4,909	75,506
Derivative Asset, Noncurrent	2,152	25,449
Liabilities:
Commodity derivative liabilities – current	(60,593)	81,451
Derivative Liability, Noncurrent	(21,416)	(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	(2,496)
Derivative Liability, Noncurrent	0
Fair Value, Measurements, Recurring | Interest Rate Swap | Level 1
Liabilities:
Commodity derivative liabilities – current	0	0
Derivative Liability, Noncurrent	0	0
Fair Value, Measurements, Recurring | Interest Rate Swap | Level 2
Liabilities:
Commodity derivative liabilities – current	(2,496)	(3,655)
Derivative Liability, Noncurrent	0	(1,645)
Fair Value, Measurements, Recurring | Interest Rate Swap | Level 3
Liabilities:
Commodity derivative liabilities – current	0	0
Derivative Liability, Noncurrent	$ 0	$ 0
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