Financial Instruments and Risk Management (Effect of Derivative Instruments on the Condensed Consolidated Balance Sheets Fair Values of Derivative Instruments Derivatives Not Designated As Hedging Instrument) (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Derivatives, Fair Value [Line Items]
Fair value of financial instruments	$ 51.1	$ 43.3
Fair value of financial instruments	17.1	12.9
Not Designated as Hedging Instruments
Derivatives, Fair Value [Line Items]
Fair value of financial instruments	38.6	8.5
Not Designated as Hedging Instruments | Prepaid expenses and other current assets | Foreign currency forward contracts
Derivatives, Fair Value [Line Items]
Fair value of financial instruments	38.6	8.5
Not Designated as Hedging Instruments | Other current liabilities | Foreign currency forward contracts
Derivatives, Fair Value [Line Items]
Fair value of financial instruments	$ 17.1	$ 12.9