Fixed Assets (Details) - USD ($) $ in Millions	Dec. 31, 2025	Dec. 31, 2024
Property, Plant and Equipment [Line Items]
Fixed assets, at cost	$ 213.1	$ 213.6
Accumulated depreciation and amortization	(158.7)	(156.0)
Fixed assets (net)	54.4	57.6
Buildings and leasehold improvements
Property, Plant and Equipment [Line Items]
Fixed assets, at cost	112.4	110.0
Software
Property, Plant and Equipment [Line Items]
Fixed assets, at cost	43.5	45.2
Office equipment
Property, Plant and Equipment [Line Items]
Fixed assets, at cost	18.7	20.2
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Fixed assets, at cost	17.6	17.5
Land, improvements and other
Property, Plant and Equipment [Line Items]
Fixed assets, at cost	$ 20.9	$ 20.7