Retirement Plans - Components of Net Periodic Pension Benefit Cost and Other Changes in Plan Assets and Obligations Recognized in Earnings and Other Comprehensive Earnings (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Net periodic pension cost:
Service cost	$ 3.3	$ 0.5	$ 0.5
Interest cost on benefit obligation	10.7	6.8	6.4
Expected return on plan assets	$ (14.2)	$ (19.1)	$ (17.7)
Defined Benefit Plan, Net Periodic Benefit (Cost) Credit, Expected Return (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Labor and Related Expense	Labor and Related Expense	Labor and Related Expense
Amortization of net loss	$ 4.9	$ 2.4	$ 5.9
Defined Benefit Plan, Net Periodic Benefit (Cost) Credit, Amortization of Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Labor and Related Expense	Labor and Related Expense	Labor and Related Expense
Net periodic benefit income	$ 4.7	$ (9.4)	$ (4.9)
Other changes in plan assets and obligations recognized in other comprehensive earnings:
Net loss (gain) incurred	(12.0)	14.1	(19.9)
Amortization of net loss	(4.9)	(2.4)	(5.9)
Total recognized in other comprehensive income (loss)	(16.9)	11.7	(25.8)
Total recognized in net periodic pension cost and other comprehensive income (loss)	$ (12.2)	$ 2.3	$ (30.7)