Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.

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Face (par) amount of debt instrument at time of issuance.

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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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The estimated value of gains (losses), net anticipated to be transferred in the future from accumulated other comprehensive income into earnings.

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Derivatives and Hedging Activities - Narrative (Details) $ in Millions	3 Months Ended
	Mar. 31, 2018 USD ($) derivative	Mar. 31, 2017 USD ($)	Dec. 31, 2017 derivative	Jun. 30, 2015 EUR (€)	Mar. 31, 2015 USD ($)
Derivative [Line Items]
Net unrealized after-tax losses related to contracts included in AOCI	$ 9.9	$ 9.6
4.50% Senior Notes due September 2023
Derivative [Line Items]
Debt interest rate	4.50%
Foreign currency forward contracts \| Net Investment Hedge
Derivative [Line Items]
Notional amount of outstanding derivative \| €				€ 270,000,000
Cumulative translation adjustment loss before tax	$ 3.5
Cumulative translation adjustment loss, after tax	$ 2.2
Foreign currency forward contracts \| Designated as Hedging Instruments
Derivative [Line Items]
Maximum original maturity of foreign currency forward contracts	12 months
Net unrealized after-tax losses related to contracts included in AOCI	$ (1.1)	$ 2.9
Net unrealized derivative losses included in AOCI to be reclassified into earnings in next twelve months	$ (0.3)
Foreign currency forward contracts \| Derivatives not designated as hedging instruments
Derivative [Line Items]
Maximum original maturity of foreign currency forward contracts	12 months
Interest rate swaps
Derivative [Line Items]
Number of derivative instruments outstanding \| derivative	0		0
EUR - Denominated debt \| Net Investment Hedge \| 4.50% Senior Notes due September 2023
Derivative [Line Items]
Debt instrument face amount \| €				€ 400,000,000
Debt interest rate				4.50%
EUR - Denominated debt \| Designated as Hedging Instruments \| Net Investment Hedge
Derivative [Line Items]
Fair value of liability derivatives	$ 42.1
Fair value of liability derivatives, after tax	27.9
Cross-currency swaps \| Net Investment Hedge
Derivative [Line Items]
Notional amount of outstanding derivative					$ 425.0
Cross-currency swaps \| Designated as Hedging Instruments \| Net Investment Hedge
Derivative [Line Items]
Fair value of liability derivatives	61.9
Semi-annual interest settlement resulted in AOCI	17.7
Semi-annual interest settlement resulted in AOCI after tax	$ (44.2)