Allowance for Expected Credit Losses - Reinsurance recoverables (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Credit Loss [Abstract]
Balance at beginning of period	$ 6,717	$ 5,939	$ 6,564	$ 5,881
Balance at end of period	6,821	6,356	6,821	6,356
Allowance for Expected Credit Losses
Balance at beginning of period	22	15	22	13
Change for provision of expected credit losses	1	2	1	4
Balance at end of period	$ 23	$ 17	$ 23	$ 17