Derivative Financial Instruments and Risk Management - Derivative Liabilities at Fair Value (Details) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Liabilities	$ 6.7	$ 5.5
Gross Amounts Offset in the Consolidated Balance Sheets	0.0	0.0
Net Presented in the Consolidated Balance Sheets	6.7	5.5
Amount Subject to Master Netting Agreement	(4.0)	(1.3)
Net Amount	$ 2.7	$ 4.2

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 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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Fair value of asset associated with 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.

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Fair value, after effects of master netting arrangements, deduction of liabilities not subject to a master netting arrangement and elected not to be offset, 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, offset against the right to receive collateral.

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Fair value 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 offset, deducted from derivative liabilities.

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