Quarterly report pursuant to Section 13 or 15(d)

Fair Value of Derivative Instruments on Condensed Consolidated Balance Sheets (Detail)

v3.8.0.1
Fair Value of Derivative Instruments on Condensed Consolidated Balance Sheets (Detail) - USD ($)
$ in Thousands
Sep. 30, 2017
Dec. 31, 2016
Derivatives, Fair Value [Line Items]    
Derivative assets, current $ 6,140 $ 0
Derivative Asset, Noncurrent 2,520 0
Derivative assets 8,660 0
Commodity derivative liabilities – current 13,634 12,932
Derivative Liability, Noncurrent 4,923 14,437
Derivative Liability 18,557 27,369
Commodity contracts    
Derivatives, Fair Value [Line Items]    
Derivative Liability 8,700  
Commodity contracts | Derivative assets/liabilities - current    
Derivatives, Fair Value [Line Items]    
Derivative assets, current 6,140 0
Commodity derivative liabilities – current 13,634 12,932
Commodity contracts | Noncurrent Derivative Contract [Member]    
Derivatives, Fair Value [Line Items]    
Derivative Asset, Noncurrent 2,520 0
Derivative Liability, Noncurrent $ 4,923 $ 14,437