10-K Business Optimization Initiatives (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Business Optimization Initiatives [Line Items]
Business optimization initiatives, incurred cost	$ 730		$ 39	$ 202	$ 653
Business Optimization, Incurred Cost, Statement of Income or Comprehensive Income [Extensible Enumeration]	Operating expense		Operating expense	Operating expense	Operating expense
Employee Termination [Member]
Business Optimization Initiatives [Line Items]
Business optimization initiatives, incurred cost					$ 197
Releases			$ (2)
Employee Termination [Member] | 2020 Business Optimization Initiatives
Business Optimization Initiatives [Line Items]
Releases		$ (33)	(2)
Property and Equipment Impairment and Abandonment [Member]
Business Optimization Initiatives [Line Items]
Business optimization initiatives, incurred cost			7	$ 66	198
Operating Lease Impairment and Abandonment [Member]
Business Optimization Initiatives [Line Items]
Business optimization initiatives, incurred cost			34	136	258
Health Benefits Segment
Business Optimization Initiatives [Line Items]
Business optimization initiatives, incurred cost			36	168	516
Health Benefits Segment | Employee Termination [Member] | 2020 Business Optimization Initiatives
Business Optimization Initiatives [Line Items]
Releases		(33)	0
CarelonRx Segment [Member]
Business Optimization Initiatives [Line Items]
Business optimization initiatives, incurred cost			0	1	4
CarelonRx Segment [Member] | Employee Termination [Member] | 2020 Business Optimization Initiatives
Business Optimization Initiatives [Line Items]
Releases		0	0
Carelon Services Segment
Business Optimization Initiatives [Line Items]
Business optimization initiatives, incurred cost			5	33	122
Carelon Services Segment | Employee Termination [Member] | 2020 Business Optimization Initiatives
Business Optimization Initiatives [Line Items]
Releases		0	0
Other [Member]
Business Optimization Initiatives [Line Items]
Business optimization initiatives, incurred cost			2	$ 0	$ 11
Other [Member] | Employee Termination [Member] | 2020 Business Optimization Initiatives
Business Optimization Initiatives [Line Items]
Releases		$ 0	$ (2)