Retirement Plans, Postretirement and Postemployment Benefits - Schedule of Funded Status (Detail) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Pension
Defined Benefit Plan Disclosure [Line Items]
Funded status of the plan at end of year	$ (109.8)	$ (130.0)
Accrued benefit cost	(109.8)	(130.0)
Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Funded status of the plan at end of year	(13.0)	(13.3)
Accrued benefit cost	$ (13.0)	$ (13.3)