Reinsurance (Summary Of Direct, Assumed And Ceded Premiums Written And Earned) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Reinsurance Disclosures [Abstract]
Direct - Premium written	$ 102,479	$ 91,579	$ 83,652
Assumed - Premium written	3,326	3,196	1,447
Ceded - Premium written	(79)	(45)	(51)
Net premiums - written	$ 105,726	$ 94,730	$ 85,048
Percentage - assumed to net premiums - written	3.10%	3.40%	1.70%
Direct - Premiums earned	$ 100,832	$ 91,131	$ 84,030
Assumed - Premium earned	3,356	3,087	1,442
Ceded - Premium earned	(79)	(45)	(51)
Premiums	$ 104,109	$ 94,173	$ 85,421
Percentage - assumed to net premiums - earned	3.20%	3.30%	1.70%