Restructuring - Restructuring Related Costs Included in Selling, General & Administrative expenses on Consolidated Statements of Income (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Restructuring Cost and Reserve [Line Items]
Restructuring costs	$ 4.9	$ 7.3	$ 38.6	$ 19.9
Severance and related costs
Restructuring Cost and Reserve [Line Items]
Restructuring costs	4.7	7.3	38.1	19.2
Other
Restructuring Cost and Reserve [Line Items]
Restructuring costs	$ 0.2	$ 0.0	$ 0.5	$ 0.7