10-K Business Acquisitions (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Sep. 30, 2023	Dec. 31, 2020
Business Acquisition [Line Items]
Goodwill, after measurement period adjustments	$ 24,383	$ 24,228	$ 25,291	$ 21,691
Health Benefits Segment
Business Acquisition [Line Items]
Goodwill, after measurement period adjustments	22,088	21,942		$ 19,924
Series of Individually Immaterial Business Acquisitions [Member]
Business Acquisition [Line Items]
Total cash considerations	752
Finite-lived Intangible Assets Acquired	89
Indefinite-lived Intangible Assets Acquired	250
Goodwill, Acquired During Period	145
Series of Individually Immaterial Business Acquisitions [Member] | Acquisition Year, Prior Year
Business Acquisition [Line Items]
Total cash considerations		$ 4,021
Finite-lived Intangible Assets Acquired	1,577
Indefinite-lived Intangible Assets Acquired	20
Goodwill, Purchase Accounting Adjustments	10
Goodwill, after measurement period adjustments	2,531
Series of Individually Immaterial Business Acquisitions [Member] | Other [Member] | Acquisition Year, Prior Year
Business Acquisition [Line Items]
Intangible Assets, Net (Including Goodwill)	795
Series of Individually Immaterial Business Acquisitions [Member] | Health Benefits Segment | Acquisition Year, Prior Year
Business Acquisition [Line Items]
Intangible Assets, Net (Including Goodwill)	$ 3,333