Quarterly report pursuant to Section 13 or 15(d)

Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail)

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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