Consolidated Statements of Comprehensive Income (Unaudited) (Parenthetical) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Other comprehensive (loss) income:
Income tax expense (benefit) on translation adjustments on net investment hedge	$ 10.6	$ (18.4)	$ 5.8	$ (21.7)
Income tax expense (benefit) on unrealized gain on investments		0.1		0.6
Income tax expense (benefit) on defined benefit pension plans and retiree health care plan	$ (0.1)	$ 0.2	0.1	$ 0.2
Income tax expense (benefit) on reclassification of unrealized cumulative gain on investments			$ (3.4)