Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Commodity derivative liabilities – current	$ 4,667	$ 12,932
Liabilities:
Derivative Liability, Noncurrent	3,694	14,437
Fair Value, Measurements, Recurring | Commodity contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Commodity derivative liabilities – current	4,667	12,932
Liabilities:
Derivative Liability, Noncurrent	3,694	14,437
Fair Value, Measurements, Recurring | Commodity contracts | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Commodity derivative liabilities – current	0	0
Liabilities:
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]
Commodity derivative liabilities – current	4,667	12,932
Liabilities:
Derivative Liability, Noncurrent	3,694	14,437
Fair Value, Measurements, Recurring | Commodity contracts | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Commodity derivative liabilities – current	0	0
Liabilities:
Derivative Liability, Noncurrent	$ 0	$ 0