Derivatives Offsetting (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Derivative Asset, Fair Value, Amount Offset Against Collateral [Abstract]
Gross Amount of Recognized Assets		$ 0.4
Net Amount of Assets presented in the Consolidated Balance Sheets		0.4
Financial Instruments, Gross Amounts Not Offset in the Consolidated Balance Sheets, Derivative Assets		(0.3)
Cash Collateral Received, Gross Amounts Not Offset in the Consolidated Balance Sheets, Derivative Asset		0
Net Amount, Derivative Asset		0.1us-gaap_DerivativeAssets
Derivative Liability, Fair Value, Amount Offset Against Collateral [Abstract]
Gross Amount of Recognized Liabilities, Derivatives	83.2	77.2
Net Amount of Liabilities, Derivatives, Amount Not Offset Against Collateral	83.2	77.2
Financial Instruments, Gross Amounts Not Offset in the Consolidated Balance Sheets, Derivative Liabilities	0	(0.3)
Cash Collateral Received, Gross Amounts Not Offset in the Consolidated Balance Sheets, Derivative Liabilities	0	0
Net Amount, Derivative Liabilities	$ 83.2us-gaap_DerivativeLiabilities	$ 76.9us-gaap_DerivativeLiabilities

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Fair value of securities received as collateral against derivative assets.

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Fair value of 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, not subject to a master netting arrangement.

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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. Includes assets not subject to a master netting arrangement and not elected to be offset.

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Fair value, after effects of master netting arrangements, of 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 offset against an obligation to return collateral. Includes assets not subject to a master netting arrangement and not elected to be offset.

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Fair value, before 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 elected not to be offset. Excludes liabilities not subject to a master netting arrangement.

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Fair value, after offset of derivative asset, of 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, elected not to be and before offset against a right to receive collateral under a master netting arrangement. Includes liabilities elected not to be offset. Excludes liabilities not subject to a master netting arrangement.

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Fair value of securities pledged as collateral against derivative liabilities.

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