Components of Accumulated Other Comprehensive Income Before Tax (Detail) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Pension Plans, Defined Benefit | U.S. Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss (gain)	$ 61.5	$ 63.1
Prior service cost	0.0	0.1
Total accumulated other comprehensive loss (income) recognized in the balance sheet	61.5	63.2	$ 48.1
Pension Plans, Defined Benefit | Non-U.S. Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss (gain)	41.9	47.6
Prior service cost	3.5	3.7
Total accumulated other comprehensive loss (income) recognized in the balance sheet	45.4	51.3	$ 33.9
Postretirement Benefits Other Than Pensions | U.S. Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss (gain)	(0.1)	2.0
Prior service cost	4.0	6.1
Total accumulated other comprehensive loss (income) recognized in the balance sheet	$ 3.9	$ 8.1