Investments - Net Investment Gains (Losses) By Transaction Type (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Investments, Debt and Equity Securities [Abstract]
Credit loss impairments	$ (1.2)	$ 0.3	$ (0.4)
Intent-to-sell impairments	(5.3)	(0.2)	(6.7)
Total impairments	(6.5)	0.1	(7.1)
Sales and other, net	8.4	(24.3)	(25.0)
Change in fair value - equity securities	(2.1)	7.4	7.9
Change in fair value and losses realized on settlements - derivatives	(12.8)	(0.5)	0.2
Net investment losses	$ (13.0)	$ (17.3)	$ (24.0)