Reinsurance and Indemnification - Schedule of Effects of Reinsurance Ceded and Indemnification Programs on Property and Casualty Insurance Claims and Claims Expense and Accident, Health and Other Policy Benefits (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Property and casualty insurance claims and claims expense
Reductions to costs and expenses due to reinsurance ceded amounts
Ceded losses incurred	$ (662)	$ (274)	$ (1,178)	$ (534)
Accident, health and other policy benefits
Reductions to costs and expenses due to reinsurance ceded amounts
Ceded losses incurred	$ (13)	$ (7)	$ (27)	$ (32)