Short-Duration Insurance Contracts - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Segment Reporting Information [Line Items]
Automobile liability coverage percent reserves	68.00%
Percentage of losses incurred	99.70%
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	0.0	$ (22.0)	$ 7.2
Unfavorable development of total reserves for claims occurring in prior years		28.0
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	$ 13.9