Fair Value Measurement - Financial Assets and Liabilities by Hierarchy Level (Details) - USD ($) $ in Millions		Jun. 30, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds	[1]	$ 62.3	$ 126.9
Available for sale investments		51.6	58.4
Trading securities		15.9	13.8
Deferred compensation plan liabilities		(15.9)	(13.8)
Derivatives:
Forward exchange contracts-Assets	[2]	1.6	0.2
Forward exchange contracts-(Liabilities)	[3]	0.0	(0.7)
TOTAL		115.5	184.8
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	[1]	62.3	126.9
Available for sale investments		0.0	0.0
Trading securities		15.9	13.8
Deferred compensation plan liabilities		(15.9)	(13.8)
Derivatives:
Forward exchange contracts-Assets	[2]	0.0	0.0
Forward exchange contracts-(Liabilities)	[3]	0.0	0.0
TOTAL		62.3	126.9
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	[1]	0.0	0.0
Available for sale investments		47.7	54.3
Trading securities		0.0	0.0
Deferred compensation plan liabilities		0.0	0.0
Derivatives:
Forward exchange contracts-Assets	[2]	1.6	0.2
Forward exchange contracts-(Liabilities)	[3]	0.0	(0.7)
TOTAL		49.3	53.8
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	[1]	0.0	0.0
Available for sale investments		3.9	4.1
Trading securities		0.0	0.0
Deferred compensation plan liabilities		0.0	0.0
Derivatives:
Forward exchange contracts-Assets	[2]	0.0	0.0
Forward exchange contracts-(Liabilities)	[3]	0.0	0.0
TOTAL		$ 3.9	$ 4.1

[1] Money market funds are reflected in Cash and cash equivalents in the Condensed Consolidated Balance Sheet.

[2] Forward exchange contracts-Assets are reflected in Other current assets in the Condensed Consolidated Balance Sheet.

[3] Forward exchange contracts-(Liabilities) are reflected in Other accrued liabilities in the Condensed Consolidated Balance Sheet.