Retirement Plans, Postretirement and Postemployment Benefits - Net Periodic Benefit Credit or Cost Not Yet Recognized (Detail) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Pension
Defined Benefit Plan Disclosure [Line Items]
Prior service cost (credit) - Gross	$ 5.1	$ 5.8
Actuarial (gain) loss - Gross	166.2	245.9
Total - Gross	171.3	251.7
Prior service cost (credit) - Net of tax	3.0	3.7
Actuarial (gain) loss - Net of tax	97.0	157.1
Total - Net of tax	100.0	160.8
Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Prior service cost (credit) - Gross	(1.5)	(2.2)
Actuarial (gain) loss - Gross	(2.4)	(2.0)
Total - Gross	(3.9)	(4.2)
Prior service cost (credit) - Net of tax	(0.9)	(1.4)
Actuarial (gain) loss - Net of tax	(1.4)	(1.3)
Total - Net of tax	$ (2.3)	$ (2.7)