Reinsurance and Indemnification - Schedule of Rollforward of Credit Loss Allowance for Reinsurance Recoverables (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
Reinsurance Recoverable, Allowance for Credit Loss [Roll Forward]
Beginning balance	$ (61)	$ (66)	$ (62)	$ (66)
(Increase) decrease in the provision for credit losses	0	(5)	1	(5)
Write-offs	0	9	0	9
Ending balance	(61)	(62)	(61)	(62)
Accident and health insurance
Reinsurance Recoverable, Allowance for Credit Loss [Roll Forward]
Beginning balance	(3)	(8)	(3)	(8)
(Increase) decrease in the provision for credit losses	0	0	0	0
Write-offs	0	0	0	0
Ending balance	$ (3)	$ (8)	$ (3)	$ (8)