10-K Reinsurance (Summary Of Direct, Assumed And Ceded Premiums Earned) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Reinsurance Disclosures [Abstract]
Direct - Premiums earned					$ 128,867	$ 113,149	$ 100,832
Assumed - Premium earned					4,426	4,298	3,356
Ceded - Premium earned					(64)	(74)	(79)
Premiums	$ 35,259	$ 33,722	$ 107,716	$ 99,583	$ 133,229	$ 117,373	$ 104,109
Percentage - assumed to net premiums - earned					3.30%	3.70%	3.20%