Reinsurance and Indemnification - Schedule of Effects of Reinsurance Ceded and Indemnification Programs on Property and Casualty Premiums Earned and Accident and Health Insurance Premiums and Contract Charges (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Property and casualty insurance premiums earned
Reinsurance
Property and casualty insurance premiums earned	$ (640)	$ (552)	$ (1,791)	$ (1,697)
Accident and health insurance premiums and contract charges
Reinsurance
Accident and health insurance premiums and contract charges	$ (122)	$ (16)	$ (145)	$ (37)