Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Assets:
Commodity derivative assets – current	$ 78,793	$ 4,131
Derivative assets	25,449	2,750
Liabilities:
Derivative liabilities, current	85,427	23,450
Derivative liabilities, noncurrent	(28,434)	(3,385)
Fair Value, Measurements, Recurring | Commodity contracts
Assets:
Commodity derivative assets – current	78,793	4,131
Derivative assets	25,449	2,750
Liabilities:
Derivative liabilities, current	(81,772)	(23,450)
Derivative liabilities, noncurrent	(26,789)	(3,385)
Fair Value, Measurements, Recurring | Commodity contracts | Level 1
Assets:
Commodity derivative assets – current	0	0
Derivative assets	0	0
Liabilities:
Derivative liabilities, current	0	0
Derivative liabilities, noncurrent	0	0
Fair Value, Measurements, Recurring | Commodity contracts | Level 2
Assets:
Commodity derivative assets – current	78,793	4,131
Derivative assets	25,449	2,750
Liabilities:
Derivative liabilities, current	(81,772)	(23,450)
Derivative liabilities, noncurrent	(26,789)	(3,385)
Fair Value, Measurements, Recurring | Commodity contracts | Level 3
Assets:
Commodity derivative assets – current	0	0
Derivative assets	0	0
Liabilities:
Derivative liabilities, current	0	0
Derivative liabilities, noncurrent	0	$ 0
Fair Value, Measurements, Recurring | Interest Rate Swap
Liabilities:
Derivative liabilities, current	(3,655)
Derivative liabilities, noncurrent	(1,645)
Fair Value, Measurements, Recurring | Interest Rate Swap | Level 1
Liabilities:
Derivative liabilities, current	0
Derivative liabilities, noncurrent	0
Fair Value, Measurements, Recurring | Interest Rate Swap | Level 2
Liabilities:
Derivative liabilities, current	(3,655)
Derivative liabilities, noncurrent	(1,645)
Fair Value, Measurements, Recurring | Interest Rate Swap | Level 3
Liabilities:
Derivative liabilities, current	0
Derivative liabilities, noncurrent	$ 0
Crude Oil | Commodity contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative, Underlying Basis	WTI
MEH [Domain] | Commodity contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative, Underlying Basis	MEH