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	Sep. 30, 2018	Dec. 31, 2017
Derivatives, Fair Value [Line Items]
Fair value of financial instruments	$ 7.1	$ 88.9
Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Fair value of financial instruments	0.0	79.6
Fair value of financial instruments	87.9	0.0
Designated as Hedging Instrument | Prepaid expenses and other current assets | Interest rate swaps
Derivatives, Fair Value [Line Items]
Fair value of financial instruments	0.0	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	0.0	63.4
Designated as Hedging Instrument | Prepaid expenses and other current assets | Interest rate swaps
Derivatives, Fair Value [Line Items]
Fair value of financial instruments	11.1	0.0
Designated as Hedging Instrument | Prepaid expenses and other current assets | Foreign exchange forward contracts
Derivatives, Fair Value [Line Items]
Fair value of financial instruments	$ 76.8	$ 0.0