Investments - Sales of Fixed Maturity and Equity Securities (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Summary of fair value and gross unrealized losses of fixed maturity securities and equity securities in an unrealized loss position
Proceeds received	$ 465.5	$ 424.8	$ 377.6
Gross gains realized	5.4	4.0	2.2
Gross losses realized	(4.9)	(19.0)	(14.0)
Equity securities
Proceeds received	17.3	16.3	18.7
Gross gains realized	0.9	0.0	0.0
Gross losses realized	$ (0.1)	$ (7.8)	$ (11.8)