Short-Duration Insurance Contracts - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Segment Reporting Information [Line Items]
Automobile liability coverage percent reserves	68.00%
Annual percentage payout as a percent of property & casualty incurred losses (as a percent)	94.00%
Potential variability of property and casualty loss reserves	1.00%
Probability of other possible outcomes possible impact on net income	$ 2.5
Sensitivity analysis, hypothetical change in loss ratio, percent	1.00%
Sensitivity analysis, hypothetical change in loss ratio, amount	$ 0.8
Property & Casualty
Segment Reporting Information [Line Items]
Favorable (unfavorable) development of total reserves for claims occurring in prior years, net	11.8	$ 0.0	$ (22.0)
Unfavorable development of total reserves for claims occurring in prior years			(28.0)
Favorable loss trends in auto and homeowners	29.5
Favorable development of total reserves recognition of loss reserves for legacy commercial lines	17.7
Favorable development of total reserves for claims occurring in prior years			$ 6.0
Group benefits
Segment Reporting Information [Line Items]
Favorable (unfavorable) development of total reserves for claims occurring in prior years, net	$ 14.5	$ 13.9