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
	Mar. 31, 2025	Mar. 31, 2024
Property and casualty insurance claims and claims expense
Reductions to costs and expenses due to reinsurance ceded amounts
Ceded losses incurred	$ (1,685)	$ (232)
Accident, health and other policy benefits
Reductions to costs and expenses due to reinsurance ceded amounts
Ceded losses incurred	$ (19)	$ (6)