Fair Value Measurement - Narrative (Details) $ in Millions	3 Months Ended
	Mar. 31, 2018 USD ($) contract	Mar. 31, 2017 USD ($)	Dec. 31, 2017 USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale investments	$ 57.1		$ 58.4
Trading securities	14.9		13.8
Purchase of trading securities related to deferred compensation plans	1.6	$ 1.6
Proceeds from securities sold	$ 0.4	$ 0.3
Number of foreign exchange contracts held (in contracts) | contract	43
Long-term debt, fair value	$ 1,920.6		1,013.2
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	14.9		$ 13.8
Forward exchange contract
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative, notional amount	$ 37.0