Fair Value Measurement Financial Assets and Liabilities by Hierarchy Level (Details) - USD ($) $ in Millions	Sep. 30, 2015	Dec. 31, 2014
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds	$ 264.4	$ 365.9
Available for sale investments	47.9	43.0
Trading securities	9.3	8.9
Deferred compensation plan liabilities	(9.3)	(8.9)
Derivatives:
Forward exchange contracts-Assets	1.3	0.7
Forward exchange contracts-(Liabilities)	0.0	0.0
Total	313.6	409.6
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	264.4	365.9
Available for sale investments	0.0	0.0
Trading securities	9.3	8.9
Deferred compensation plan liabilities	(9.3)	(8.9)
Derivatives:
Forward exchange contracts-Assets	0.0	0.0
Forward exchange contracts-(Liabilities)	0.0	0.0
Total	264.4	365.9
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	0.0	0.0
Available for sale investments	43.1	43.0
Trading securities	0.0	0.0
Deferred compensation plan liabilities	0.0	0.0
Derivatives:
Forward exchange contracts-Assets	1.3	0.7
Forward exchange contracts-(Liabilities)	0.0	0.0
Total	44.4	43.7
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
Available for sale investments	4.8	0.0
Trading securities	0.0	0.0
Deferred compensation plan liabilities	0.0	0.0
Derivatives:
Forward exchange contracts-Assets	0.0	0.0
Forward exchange contracts-(Liabilities)	0.0	0.0
Total	$ 4.8	$ 0.0