Buildings and Equipment (Detail) - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023
Property, Plant and Equipment [Line Items]
ORIGINAL COST	$ 1,331.1	$ 1,331.1
ACCUMULATED DEPRECIATION	840.8	828.9
NET BOOK VALUE	490.3	502.2
Land and Improvements
Property, Plant and Equipment [Line Items]
ORIGINAL COST	11.5	11.5
ACCUMULATED DEPRECIATION	0.3	0.3
NET BOOK VALUE	11.2	11.2
Buildings
Property, Plant and Equipment [Line Items]
ORIGINAL COST	226.5	253.1
ACCUMULATED DEPRECIATION	143.4	141.4
NET BOOK VALUE	83.1	111.7
Equipment
Property, Plant and Equipment [Line Items]
ORIGINAL COST	539.6	536.5
ACCUMULATED DEPRECIATION	343.4	337.5
NET BOOK VALUE	196.2	199.0
Leasehold Improvements
Property, Plant and Equipment [Line Items]
ORIGINAL COST	553.5	530.0
ACCUMULATED DEPRECIATION	353.7	349.7
NET BOOK VALUE	$ 199.8	$ 180.3