Financial Instruments and Risk Management (Effect of Derivative Instruments on the Condensed Consolidated Balance Sheets Fair Value of Derivative Instruments Derivatives Designated As Hedging Instruments) (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Derivatives, Fair Value [Line Items]
Fair value of financial instruments	$ 69.6	$ 88.9
Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Fair value of financial instruments	39.0	79.6
Designated as Hedging Instrument | Prepaid expenses and other current assets | Interest rate swaps
Derivatives, Fair Value [Line Items]
Fair value of financial instruments	0.2	16.2
Designated as Hedging Instrument | Prepaid expenses and other current assets | Foreign exchange forward contracts
Derivatives, Fair Value [Line Items]
Fair value of financial instruments	$ 38.8	$ 63.4