CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement Of Income And Comprehensive Income [Abstract]
Net Income	$ 743.4	$ 459.0	$ 410.4
Other comprehensive income, net of tax:
Foreign exchange translation adjustments	18.4	(11.5)	(22.1)
Defined benefit plan adjustments gain (loss)	12.6	(1.7)	6.2
Income (loss) from derivative agreements	(3.6)	(4.7)	4.7
Other comprehensive (loss) income	27.4	(17.9)	(11.2)
Comprehensive income	$ 770.8	$ 441.1	$ 399.2