Employee Benefits - Net Periodic Postretirement (Benefit) Expense (Detail) - Other Postretirement Plan - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Aug. 31, 2020	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Defined Benefit Plan Disclosure [Line Items]
Service Cost		$ 0.0	$ 0.0	$ 0.0
Interest Cost		0.3	0.3	0.7
Expected Return on Plan Assets		0.0	0.0	0.0
Amortization
Net Actuarial (Gain) Loss		(0.3)	(0.2)	(0.6)
Prior Service (Credit) Cost	$ 12.7	(0.9)	(0.9)	(0.3)
Net Periodic Pension Expense		$ (0.9)	$ (0.8)	$ (0.2)