10-Q Medical Claims Payable Medical Claims Payable (Reconciliation of the Claims Development to the Claims Liability) (Details) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022	Sep. 30, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
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