Derivative Instruments - Schedule of Location and Fair Value of Outstanding Commodity Derivative Instruments (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Derivatives, Fair Value [Line Items]
Derivative instruments — current assets	$ 253,320us-gaap_DerivativeAssetsCurrent	$ 302,159us-gaap_DerivativeAssetsCurrent
Derivative instruments — non-current assets	0us-gaap_DerivativeAssetsNoncurrent	13,348us-gaap_DerivativeAssetsNoncurrent
Total derivative instruments	253,320
Crude oil [Member]
Derivatives, Fair Value [Line Items]
Derivative instruments — current assets	253,320	302,159
Derivative instruments — non-current assets	0	13,348
Total derivative instruments	$ 253,320	$ 315,507

Fair value, after the effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset, expected to be settled within one year or normal operating cycle, if longer. Includes assets not subject to a master netting arrangement and not elected to be offset.

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Fair value, after the effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset, expected to be settled after one year or the normal operating cycle, if longer. Includes assets not subject to a master netting arrangement and not elected to be offset.

+ References+ Details