Employee Benefits - Change in Accumulated Postretirement Benefit Obligation (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Actuarial (Gain) Loss	$ (365.5)	$ (31.5)
Other Postretirement Plan
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Beginning Balance	10.2	15.7
Service Cost	0.0	0.0	$ 0.0
Interest Cost	0.3	0.3	0.7
Plan Amendment	0.0	0.0
Actuarial (Gain) Loss	1.6	(3.3)
Net Claims Paid	(3.3)	(2.5)
Ending Balance	$ 8.8	$ 10.2	$ 15.7