Fair Value Measurments (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Derivative Assets Abstract
Derivative assets	$ 104,190us-gaap_DerivativeAssetsCurrent	$ 1,415us-gaap_DerivativeAssetsCurrent
Derivative Liabilities Abstract
Derivative liabilities	0us-gaap_DerivativeLiabilitiesCurrent	27,291us-gaap_DerivativeLiabilitiesCurrent
Fair Value Inputs Level 2 [Member]
Derivative Assets Abstract
Derivative assets	$ 104,190

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 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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