Components of Accumulated Other Comprehensive Income Before Tax (Detail) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
U.S. Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss (gain)	$ 56.2	$ 95.6
Prior service cost (credit)	0.1	0.3
Total accumulated other comprehensive income recognized in the balance sheet	56.3	95.9	$ 79.3
Non-U.S. Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss (gain)	39.1	35.7
Prior service cost (credit)	3.7	3.8
Total accumulated other comprehensive income recognized in the balance sheet	42.8	39.5	$ 34.2
U.S. Postretirement Benefit Plans
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss (gain)	(3.7)	(4.8)
Prior service cost (credit)	(10.6)	(12.8)
Total accumulated other comprehensive income recognized in the balance sheet	(14.3)	(17.6)
Non-U.S. Postretirement Benefit Plan
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss (gain)	1.5	(1.5)
Prior service cost (credit)	(0.4)	0.2
Total accumulated other comprehensive income recognized in the balance sheet	$ 1.1	$ (1.3)