Components of Pension Expense (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Defined Benefit Plan Net Periodic Benefit Cost [Abstract]
Service cost	$ 148.4	$ 130.4	$ 102.0
Interest on projected benefit obligation	65.3	83.0	95.6
Expected return on assets	(203.3)	(190.6)	(176.6)
Amortization of prior service costs	0.8	1.5	1.4
Recognized actuarial loss	58.7	44.2	20.5
Settlement loss		11.6
Net pension expense	$ 69.9	$ 80.1	$ 42.9