Defined Benefit and Postretirement Benefits (Components Of Net Periodic Cost) (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Pension
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 1.3	$ 1.5
Interest cost	5.2	5.1
Expected return on plan assets	(13.9)	(14.1)
Recognized curtailment gain		(0.7)
Amortization of prior service cost	0.0	0.0
Amortization of net loss	4.8	6.5
Net periodic cost	(2.6)	(1.7)
Postretirement
Defined Benefit Plan Disclosure [Line Items]
Service cost	0.1	0.1
Interest cost	0.2	0.2
Expected return on plan assets	0.0	0.0
Amortization of prior service cost	(0.3)	(0.3)
Amortization of net loss	0.0	0.0
Net periodic cost	$ 0.0	$ 0.0