Derivative Instruments (Details 2) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Fair value of derivative instruments
Current portion of fair value of derivative assets	$ 692,554us-gaap_DerivativeAssetsCurrent	$ 183,000us-gaap_DerivativeAssetsCurrent
Noncurrent portion of fair value of derivative assets	899,997us-gaap_DerivativeAssetsNoncurrent	677,780us-gaap_DerivativeAssetsNoncurrent
Total asset derivatives	1,592,551us-gaap_DerivativeAssets	860,780us-gaap_DerivativeAssets
Current portion of fair value of derivative liability		646us-gaap_DerivativeLiabilitiesCurrent
Total liability derivatives		646us-gaap_DerivativeLiabilities
Net derivatives	1,592,551	860,134
Net fair value of commodity derivative assets position
Fair value of derivative instruments
Total asset derivatives	1,592,551	860,780
Total liability derivatives		$ 646

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. 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 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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- Definition

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. Includes liabilities 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.

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