10-K Medical Claims Payable (Reconciliation of Net Incurred Medical Claims to Benefit Expense) (Details) - USD ($) $ in Millions	3 Months Ended						9 Months Ended		12 Months Ended
	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Medical Claims Payable (Reconciliation of Net Incurred Medical Claims to Benefit Expense) [Abstract]
Favorable (Unfavorable) Developments by Changes in Trend Factors Assumptions									$ (859)	$ (1,429)	$ (599)
Favorable (Unfavorable) Developments by Changes in Completion Factors Assumptions									(10)	(274)	(38)
Favorable (Unfavorable) Developments by Changes in Total Assumptions									(869)	(1,703)	(637)
Total net incurred medical claims	$ 29,538	$ 30,495	$ 29,683	$ 28,511	$ 27,634	$ 27,131	$ 89,716	$ 83,276	112,545	98,737	84,457
Quality Improvement And Other Claims Expense									4,097	3,834	3,588
Benefit expense	$ 30,606	$ 31,604	$ 30,786	$ 29,421	$ 28,795	$ 28,231	$ 92,996	$ 86,447	$ 116,642	$ 102,571	$ 88,045