Claim and Claim Adjustment Expense Reserves (Reconciliation of claim and claim adjustment expense reserves) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Reserves, beginning of year:
Gross	$ 22,120	$ 21,269
Ceded	5,191	4,969
Net reserves, beginning of year	16,929	16,300
Net incurred claim and claim adjustment expenses:
Provision for insured events of current year	1,326	1,188
Increase (decrease) in provision for insured events of prior years	13	(7)
Amortization of discount	11	12
Total net incurred	1,350	1,193
Net payments attributable to:
Current year events	(72)	(68)
Prior year events	(1,042)	(920)
Total net payments	(1,114)	(988)
Foreign currency translation adjustment and other	35	(92)
Net reserves, end of period	17,200	16,413
Ceded reserves, end of period	5,209	5,002
Gross reserves, end of period	$ 22,409	$ 21,415