Fair Value Measurement - Financial Assets and Liabilities by Hierarchy Level (Details) - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale investments	$ 58.5	$ 57.7
Trading securities	23.8	22.7
Deferred compensation plan liabilities	(23.8)	(22.7)
Derivatives:
Forward exchange contracts-Assets	0.1
Forward exchange contracts-(Liabilities)	(0.6)	(0.8)
TOTAL	99.5	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	23.8	22.7
Deferred compensation plan liabilities	(23.8)	(22.7)
Derivatives:
Forward exchange contracts-Assets	0.0
Forward exchange contracts-(Liabilities)	0.0	0.0
TOTAL	41.5	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	58.5	57.7
Trading securities	0.0	0.0
Deferred compensation plan liabilities	0.0	0.0
Derivatives:
Forward exchange contracts-Assets	0.1
Forward exchange contracts-(Liabilities)	(0.6)	(0.8)
TOTAL	58.0	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	41.5	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	41.5	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