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
3 Months Ended
Mar. 31, 2019
Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Document Period End Date Mar. 31, 2019  
Derivative Asset, Current $ 2,658 $ 34,932
Derivative Asset, Noncurrent 229 10,100
Liabilities:    
Commodity derivative liabilities – current 25,107 991
Derivative Liability, Noncurrent 6,150 0
Fair Value, Measurements, Recurring | Commodity contracts    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Derivative Asset, Current 2,658 34,932
Derivative Asset, Noncurrent 229 10,100
Liabilities:    
Commodity derivative liabilities – current (25,107) (991)
Derivative Liability, Noncurrent 6,150 0
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 2,658 34,932
Derivative Asset, Noncurrent 229 10,100
Liabilities:    
Commodity derivative liabilities – current (25,107) (991)
Derivative Liability, Noncurrent 6,150 0
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
Crude Oil | Commodity contracts    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Third-party quoted forward prices WTI  
Louisiana Light Sweet [Member] | Commodity contracts    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Third-party quoted forward prices LLS  
MEH [Domain] | Commodity contracts    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Third-party quoted forward prices MEH