Fair Value of Derivative Instruments on Condensed Consolidated Balance Sheets (Detail) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Derivatives, Fair Value [Line Items]
Derivative assets	$ 0	$ 0
Commodity derivative liabilities – current	4,667	12,932
Derivative Liability, Noncurrent	3,694	14,437
Derivative Liability	8,361	27,369
Commodity contracts
Derivatives, Fair Value [Line Items]
Derivative Liability	8,400
Commodity contracts \| Derivative assets/liabilities - current
Derivatives, Fair Value [Line Items]
Derivative assets, current	0	0
Commodity derivative liabilities – current	4,667	12,932
Commodity contracts \| Noncurrent Derivative Contract [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Noncurrent	0	0
Derivative Liability, Noncurrent	$ 3,694	$ 14,437

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