Components of Pension Expense (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Defined Benefit Plan Net Periodic Benefit Cost [Abstract]
Service cost	$ 148.5	$ 148.4	$ 130.4
Interest on projected benefit obligation	84.9	65.3	83.0
Expected return on assets	$ (215.1)	$ (203.3)	$ (190.6)
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	Costs And Expenses
Amortization of prior service costs	$ 0.7	$ 0.8	$ 1.5
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Amortization of Prior Service Cost (Credit), Statement of Income or Comprehensive Income [Extensible Enumeration]	Costs And Expenses	Costs And Expenses	Costs And Expenses
Recognized actuarial loss	$ 28.9	$ 58.7	$ 44.2
Settlement loss			$ 11.6
Defined Benefit Plan, Net Periodic Benefit (Cost) Credit, Settlement Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Costs And Expenses	Costs And Expenses	Costs And Expenses
Net pension expense	$ 47.9	$ 69.9	$ 80.1