Income from Investments - Net Impairment Losses Recognized in Earnings (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Net Investment Income [Line Items]
Impairment Losses	$ (5.8)	$ (1.1)	$ (25.8)
Available for sale, debt securities, other than temporary impairment loss	3.3	2.0	23.8
Fixed Maturities:
Net Investment Income [Line Items]
Impairment Losses	(4.8)	(0.1)	(25.8)
Equity Securities
Net Investment Income [Line Items]
Impairment Losses	(0.4)	(0.5)	0.0
Real Estate
Net Investment Income [Line Items]
Impairment Losses	(0.4)	0.0	0.0
Other Long-Term Investments
Net Investment Income [Line Items]
Impairment Losses	$ (0.2)	$ (0.5)	$ 0.0