Derivatives and Hedging Activities - Narrative (Details) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018 USD ($) derivative	Sep. 30, 2017 USD ($)	Sep. 30, 2018 USD ($) derivative	Sep. 30, 2017 USD ($)	Dec. 31, 2017 derivative	Jun. 30, 2015 EUR (€)	Mar. 31, 2015 USD ($)
Derivative [Line Items]
Unrealized (loss) gain on derivative instruments, net of taxes (less than in current QTD)	$ (2.2)	$ (21.6)	$ 11.5	$ (72.2)
4.50% Senior Notes due September 2023
Derivative [Line Items]
Debt interest rate	4.50%		4.50%
Foreign currency forward contracts | Designated as Hedging Instruments
Derivative [Line Items]
Maximum original maturity of foreign currency forward contracts			12 months
Unrealized (loss) gain on derivative instruments, net of taxes (less than in current QTD)	$ (1.0)	(1.6)	$ 2.5	(6.1)
Net unrealized derivative gains included in AOCI to be reclassified into earnings in next twelve months			$ 1.0
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		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	$ 15.7		$ 15.7
Fair value of liability derivatives, after tax	$ 8.1		$ 8.1
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		61.9
Semi-annual interest settlement resulted in AOCI				17.7
Semi-annual interest settlement resulted in AOCI after tax				$ (44.2)