Allowance for Expected Credit Losses - Reinsurance recoverables (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Credit Loss [Abstract]
Balance at beginning of period	$ 6,564	$ 5,881
Balance at end of period	7,064	6,564
Allowance for Expected Credit Losses
Balance at beginning of period	22	13
Change for provision of expected credit losses	(1)	9
Balance at end of period	$ 21	$ 22