10-K Medical Claims Payables (Reconciliation of Short Duration Medical Claims Payable to the Consolidated Medical Claims Payable) (Details) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022	Sep. 30, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Payables and Accruals [Abstract]
Short-Duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net		$ 305,246
Short-Duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net		289,904
Net medical claims payable, end of period	$ 15,913	15,342
Ceded medical claims payable end of period	4	6	$ 3	$ 21	$ 46	$ 33
Insurance lines other than short duration	259	248
Gross medical claims payable, end of period	$ 16,176	$ 15,596		$ 13,518