Components of Net Pension (Income) Expense (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	$ 24.2	$ 27.8
Interest on projected benefit obligation	35.8	33.6
Expected return on assets	$ (62.3)	$ (60.6)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) Excluding Service Cost, Statement of Income or Comprehensive Income [Extensible Enumeration]	Costs and Expenses	Costs and Expenses
Amortization of prior service costs	$ 0.3	$ 0.3
Recognized actuarial loss	0.7	1.2
Net pension (income) expense	$ (1.3)	$ 2.3