Fair Value of Derivative Instruments on Condensed Consolidated Balance Sheets (Detail) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Derivatives, Fair Value [Line Items]
Derivative assets, current	$ 2,672	$ 0
Derivative Asset, Noncurrent	584	0
Derivative assets	3,256	0
Commodity derivative liabilities – current	0	12,932
Derivative Liability, Noncurrent	90	14,437
Derivative Liability	90	27,369
Commodity contracts
Derivatives, Fair Value [Line Items]
Derivative Liability	3,200
Commodity contracts \| Derivative assets/liabilities - current
Derivatives, Fair Value [Line Items]
Derivative assets, current	2,672	0
Commodity derivative liabilities – current	0	12,932
Commodity contracts \| Noncurrent Derivative Contract [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Noncurrent	584	0
Derivative Liability, Noncurrent	$ 90	$ 14,437

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