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, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Property and casualty insurance premiums
Reinsurance
Property and casualty insurance premiums earned	$ (514)	$ (479)	$ (1,455)	$ (1,362)
Accident and health insurance premiums and contract charges
Reinsurance
Accident and health insurance premiums and contract charges	$ (16)	$ (12)	$ (35)	$ (28)