Restructuring - Restructuring Related Costs Included in Selling, General & Administrative expenses on Consolidated Statements of Income (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Restructuring Cost and Reserve [Line Items]
Restructuring costs	$ 10.8	$ 20.9
Severance and related costs
Restructuring Cost and Reserve [Line Items]
Restructuring costs	10.6	20.6
Other
Restructuring Cost and Reserve [Line Items]
Restructuring costs	$ 0.2	$ 0.3