Derivative Instruments - Schedule of Location and Fair Value of Outstanding Commodity Derivative Instruments (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Derivatives, Fair Value [Line Items]
Derivative instruments - current assets	$ 302,159us-gaap_DerivativeAssetsCurrent	$ 2,264us-gaap_DerivativeAssetsCurrent
Derivative instruments - non-current assets	13,348us-gaap_DerivativeAssetsNoncurrent	1,333us-gaap_DerivativeAssetsNoncurrent
Derivative instruments - current liabilities	0us-gaap_DerivativeLiabilitiesCurrent	(8,188)us-gaap_DerivativeLiabilitiesCurrent
Derivative instruments - non-current liabilities	0us-gaap_DerivativeLiabilitiesNoncurrent	(139)us-gaap_DerivativeLiabilitiesNoncurrent
Total derivative instruments	315,507
Crude oil collar [Member]
Derivatives, Fair Value [Line Items]
Derivative instruments - current assets	302,159	2,264
Derivative instruments - non-current assets	13,348	1,333
Derivative instruments - current liabilities	0	(8,188)
Derivative instruments - non-current liabilities	0	(139)
Total derivative instruments	$ 315,507	$ (4,730)

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.

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- Definition

Fair value, after the effects of master netting arrangements, of a financial liability or 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.

+ References+ Details

- Definition

Fair value, after the effects of master netting arrangements, of a financial liability or 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