Short- Duration Insurance Contracts - Narrative (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Property & Casualty
Net Amount at Risk by Product and Guarantee [Line Items]
Decrease in estimated reserves for claims occurring in prior years	$ (13,000,000.0)	$ 0	$ (19,200,000)	$ 0
Favorable (unfavorable) development of total reserves for claims occurring in prior years	13,000,000	0	19,200,000	0
Group Benefits
Net Amount at Risk by Product and Guarantee [Line Items]
Decrease in estimated reserves for claims occurring in prior years	$ (3,900,000)	$ (7,600,000)	(13,200,000)	(15,500,000)
Favorable (unfavorable) development of total reserves for claims occurring in prior years			$ 13,200,000	$ 15,500,000