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	Mar. 31, 2021	Dec. 31, 2020
Derivatives, Fair Value [Line Items]
Fair value of financial instruments	$ 103.6	$ 118.6
Fair value of financial instruments	49.0	103.6
Not Designated as Hedging Instruments
Derivatives, Fair Value [Line Items]
Fair value of financial instruments	71.2	90.3
Fair value of financial instruments	49.0	102.8
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	71.2	90.3
Not Designated as Hedging Instruments | Other current liabilities | Foreign currency forward contracts
Derivatives, Fair Value [Line Items]
Fair value of financial instruments	$ 49.0	$ 102.8