Short-Duration Insurance Contracts - Schedule of Net Incurred and Paid Claims (Details) - USD ($) $ in Millions	Mar. 31, 2026	Dec. 31, 2025
Short-Duration Insurance Contracts, Historical Claims Duration [Line Items]
Unpaid claims and claim expenses	$ 573.8	$ 565.2
Total short-duration insurance contracts
Short-Duration Insurance Contracts, Historical Claims Duration [Line Items]
Unpaid claims and claim expenses	523.6	517.7
Property & Casualty
Short-Duration Insurance Contracts, Historical Claims Duration [Line Items]
Unpaid claims and claim expenses	406.9	404.5
Group Benefits
Short-Duration Insurance Contracts, Historical Claims Duration [Line Items]
Unpaid claims and claim expenses	116.7	113.2
Other than short-duration
Short-Duration Insurance Contracts, Historical Claims Duration [Line Items]
Unpaid claims and claim expenses	$ 50.2	$ 47.5