Long-Duration Insurance Contracts - Market Risk Benefits Rollforward (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Market Risk Benefit [Roll Forward]
Balance, beginning of period	$ (6.7)	$ (6.2)	$ (6.8)	$ (3.9)
Balance, beginning of period, before effects of changes in the instrument-specific credit risk	(7.0)	(6.8)	(7.4)	(4.5)
Changes in market risk benefits	(2.5)	0.3	(2.1)	(2.0)
Balance, end of period	(9.5)	(6.5)	(9.5)	(6.5)
Effect of changes in the instrument-specific credit risk	0.2	0.8	0.2	0.8
Balance, end of period	(9.3)	(5.7)	(9.3)	(5.7)
Net amount at risk	$ 12.8	$ 15.1	$ 12.8	$ 15.1
Weighted-average attained age of contract holders	62 years	62 years	62 years	62 years