Fair Value Measurement - Financial Assets and Liabilities by Hierarchy Level (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale investments	$ 58.1	$ 57.7
Trading securities	23.9	22.7
Deferred compensation plan liabilities	(23.9)	(22.7)
Derivatives:
Forward exchange contracts-Assets	0.5
Forward exchange contracts-(Liabilities)	(0.1)	(0.8)
TOTAL	109.4	83.5
Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale investments	0.0	0.0
Trading securities	23.9	22.7
Deferred compensation plan liabilities	(23.9)	(22.7)
Derivatives:
Forward exchange contracts-Assets	0.0
Forward exchange contracts-(Liabilities)	0.0	0.0
TOTAL	50.9	26.6
Quoted Prices in Active Markets for Similar Assets (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale investments	58.1	57.7
Trading securities	0.0	0.0
Deferred compensation plan liabilities	0.0	0.0
Derivatives:
Forward exchange contracts-Assets	0.5
Forward exchange contracts-(Liabilities)	(0.1)	(0.8)
TOTAL	58.5	56.9
Unobservable inputs for which little or no market data exists (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale investments	0.0	0.0
Trading securities	0.0	0.0
Deferred compensation plan liabilities	0.0	0.0
Derivatives:
Forward exchange contracts-Assets	0.0
Forward exchange contracts-(Liabilities)	0.0	0.0
TOTAL	0.0	0.0
Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds	50.9	26.6
Money market funds | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds	50.9	26.6
Money market funds | Quoted Prices in Active Markets for Similar Assets (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds	0.0	0.0
Money market funds | Unobservable inputs for which little or no market data exists (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds	$ 0.0	$ 0.0