Quarterly report pursuant to Section 13 or 15(d)

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

v3.8.0.1
Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($)
$ in Thousands
Sep. 30, 2017
Dec. 31, 2016
Assets:    
Derivative Asset, Current $ 6,140 $ 0
Derivative Asset, Noncurrent 2,520 0
Liabilities:    
Commodity derivative liabilities – current 13,634 12,932
Derivative Liability, Noncurrent 4,923 14,437
Fair Value, Measurements, Recurring | Commodity contracts    
Assets:    
Derivative Asset, Current 6,140  
Derivative Asset, Noncurrent 2,520  
Liabilities:    
Commodity derivative liabilities – current 13,634 12,932
Derivative Liability, Noncurrent 4,923 14,437
Fair Value, Measurements, Recurring | Commodity contracts | Level 1    
Assets:    
Derivative Asset, Current 0  
Derivative Asset, Noncurrent 0  
Liabilities:    
Commodity derivative liabilities – current 0 0
Derivative Liability, Noncurrent 0 0
Fair Value, Measurements, Recurring | Commodity contracts | Level 2    
Assets:    
Derivative Asset, Current 6,140  
Derivative Asset, Noncurrent 2,520  
Liabilities:    
Commodity derivative liabilities – current 13,634 12,932
Derivative Liability, Noncurrent 4,923 14,437
Fair Value, Measurements, Recurring | Commodity contracts | Level 3    
Assets:    
Derivative Asset, Current 0  
Derivative Asset, Noncurrent 0  
Liabilities:    
Commodity derivative liabilities – current 0 0
Derivative Liability, Noncurrent $ 0 $ 0