Quarterly report pursuant to Section 13 or 15(d)

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

v3.10.0.1
Fair Value of Derivative Instruments on Condensed Consolidated Balance Sheets (Detail) - USD ($)
$ in Thousands
Sep. 30, 2018
Dec. 31, 2017
Derivatives, Fair Value [Line Items]    
Derivative liabilities $ 80,641 $ 27,777
Derivative Liability, Noncurrent 37,570 13,900
Derivative Liability 118,211 41,677
Commodity contracts    
Derivatives, Fair Value [Line Items]    
Derivative Liability 118,200  
Commodity contracts | Current Derivative Contract [Member]    
Derivatives, Fair Value [Line Items]    
Derivative liabilities 80,641 27,777
Commodity contracts | Noncurrent Derivative Contract [Member]    
Derivatives, Fair Value [Line Items]    
Derivative Liability, Noncurrent $ 37,570 $ 13,900