Fair Value of Derivative Instruments on Condensed Consolidated Balance Sheets (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Derivatives, Fair Value [Line Items]
Derivative assets, current	$ 0	$ 97,956
Derivative assets	0	97,956
Derivative liabilities, noncurrent	14,437	0
Derivative liabilities, current	12,932	0
Derivative liabilities	27,369	0
Commodity contracts
Derivatives, Fair Value [Line Items]
Derivative liabilities	27,400
Commodity contracts \| Derivative assets/liabilities - current
Derivatives, Fair Value [Line Items]
Derivative assets, current	0	97,956
Derivative liabilities, current	12,932	0
Commodity contracts \| Derivative assets/liabilities - noncurrent
Derivatives, Fair Value [Line Items]
Derivative assets, noncurrent	0	0
Derivative liabilities, noncurrent	$ 14,437	$ 0

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