Components of Net Pension (Income) Expense (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Defined Benefit Plan Net Periodic Benefit Cost [Abstract]
Service cost	$ 25.0	$ 32.5
Interest on projected benefit obligation	31.1	19.1
Expected return on assets	(57.5)	(48.7)
Amortization of prior service costs	0.3	0.1
Recognized actuarial loss	0.7	5.6
Net pension (income) expense	$ (0.4)	$ 8.6