Employee Benefits - Amounts Included in Accumulated Other Comprehensive Income (Detail) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Supplemental Plan
Accumulated Other Comprehensive Income (Loss) [Line Items]
Net Actuarial Loss	$ 96.3	$ 82.5
Prior Service (Benefit) Cost	0.1	0.2
Gross Amount in Accumulated Other Comprehensive Income	96.4	82.7
Income Tax Effect	23.9	20.4
Net Amount in Accumulated Other Comprehensive Income	72.5	62.3
U.S. Plan | Pension Plans, Defined Benefit
Accumulated Other Comprehensive Income (Loss) [Line Items]
Net Actuarial Loss	332.4	426.7
Prior Service (Benefit) Cost	(0.6)	(1.0)
Gross Amount in Accumulated Other Comprehensive Income	331.8	425.7
Income Tax Effect	82.1	105.7
Net Amount in Accumulated Other Comprehensive Income	249.7	320.0
Non U.S. Plans | Pension Plans, Defined Benefit
Accumulated Other Comprehensive Income (Loss) [Line Items]
Net Actuarial Loss	49.0	46.5
Prior Service (Benefit) Cost	2.2	3.0
Gross Amount in Accumulated Other Comprehensive Income	51.2	49.5
Income Tax Effect	6.4	6.2
Net Amount in Accumulated Other Comprehensive Income	$ 44.8	$ 43.3