Retirement Plans, Postretirement and Postemployment Benefits - Schedule of Funded Status (Detail) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Defined Benefit Plan Disclosure [Line Items]
Accrued benefit credit (cost)	$ 207.6	$ 209.5
Pension
Defined Benefit Plan Disclosure [Line Items]
Funded status of the plan at end of year	207.6	209.5
Accrued benefit credit (cost)	207.6	209.5
Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Funded status of the plan at end of year	(8.3)	(8.9)
Accrued benefit credit (cost)	$ (8.3)	$ (8.9)