Contingencies and Commitments (Details) $ in Millions	3 Months Ended	9 Months Ended
	Dec. 31, 2024 USD ($)	Sep. 30, 2025 USD ($)	Dec. 31, 2023 lawsuit
Loss Contingencies [Line Items]
Number of lawsuits | lawsuit			1
After-tax costs related to non-core legacy commercial liability policies	$ 15.7	$ 7.6
Unfunded commitments to purchase investments	$ 449.9	$ 402.4