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Fair value portion of notes payable.

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Derivative Financial Instruments and Fair Value Measurements - Additional Information (Details) $ in Millions	Sep. 30, 2020 USD ($)	Sep. 30, 2020 EUR (€)	Dec. 31, 2019 USD ($)	Apr. 30, 2019 EUR (€)
Quoted Prices in Active Markets for Identical Assets (Level 1) \| Fair value measured on a recurring basis
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Deferred compensation plan assets	$ 109.7		$ 107.3
Euro-denominated notes \| Estimate of fair value measurement \| Significant Other Observable Inputs (Level 2)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Carrying value of long-term debt	1,092.8		1,062.5
Euro-denominated notes \| Carrying value \| Significant Other Observable Inputs (Level 2)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Carrying value of long-term debt	$ 1,049.6		$ 1,002.9
Cross-currency swap \| Cash flow hedge
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt \| €		€ 55,400,000		€ 202,300,000
Fixed annual interest rate	1.143%	1.143%		1.256%
Designated as hedging instrument \| Notes due September 2022 \| Euro-denominated notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	$ 467.8	€ 400,000,000.0
Designated as hedging instrument \| Notes Due June 2026 \| Euro-denominated notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	$ 581.8	€ 500,000,000.0