Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Assets:
Commodity derivative assets – current	$ 4,131	$ 34,932
Derivative assets	2,750	10,100
Liabilities:
Derivative liabilities, current	23,450	991
Derivative liabilities, noncurrent	(3,385)	0
Fair Value, Measurements, Recurring | Commodity contracts
Assets:
Commodity derivative assets – current	4,131	34,932
Derivative assets	2,750	10,100
Liabilities:
Derivative liabilities, current	(23,450)	(991)
Derivative liabilities, noncurrent	(3,385)	0
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	4,131	34,932
Derivative assets	2,750	10,100
Liabilities:
Derivative liabilities, current	(23,450)	(991)
Derivative liabilities, noncurrent	(3,385)	0
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
Crude Oil | Commodity contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative, Underlying Basis	WTI
Louisiana Light Sweet [Member] | Commodity contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative, Underlying Basis	LLS
MEH [Domain] | Commodity contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative, Underlying Basis	MEH