Restructuring Costs - Schedule of Restructuring Costs (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	$ 38.4	$ 13.0	$ 82.2	$ 41.7
Project Renewal [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring costs	7.4	(0.2)	17.7	13.0
Employee Severance, Termination Benefits and Relocation Costs [Member] | Project Renewal [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring costs	0.2	1.4	1.8	(4.0)
Exited Contractual Commitments and Other [Member] | Project Renewal [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring costs	$ 7.2	$ (1.6)	$ 15.9	$ 17.0