Restructuring and Other Charges - Reconciliation of Restructuring Liability (Detail) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Restructuring Cost and Reserve [Line Items]
Beginning Balance		$ 3.0	$ 10.9
Provision		8.3	13.9	$ 16.6
Cash Expenditures	[1]	(5.2)	(21.6)
Non-Cash Write-offs	[2]	(0.3)	(0.2)
Ending Balance		5.8	3.0	10.9
Workforce Reduction Costs [Member]
Restructuring Cost and Reserve [Line Items]
Beginning Balance		2.4	10.4
Provision		6.7	9.3
Cash Expenditures	[1]	(3.9)	(17.5)
Non-Cash Write-offs	[2]	(0.2)	0.2
Ending Balance		5.0	2.4	10.4
Asset Disposals [Member]
Restructuring Cost and Reserve [Line Items]
Provision			0.1
Non-Cash Write-offs	[2]		(0.1)
Other [Member]
Restructuring Cost and Reserve [Line Items]
Beginning Balance		0.6	0.5
Provision		1.6	4.5
Cash Expenditures	[1]	(1.3)	(4.1)
Non-Cash Write-offs	[2]	(0.1)	(0.3)
Ending Balance		$ 0.8	$ 0.6	$ 0.5

[1] Cash expenditures primarily related to severance charges.

[2] Non-cash write-offs include long-lived asset impairment charges attributable to restructuring actions.