10-K Commitments And Contingencies (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2023	Dec. 31, 2022
Commitments And Contingencies [Line Items]
Loss Contingency Accrual, Payments		$ 506
Gross premium tax rate, state of California	2.35%	2.35%
Long-term purchase commitment, amount	$ 554	$ 761
Minimum [Member]
Commitments And Contingencies [Line Items]
Aggregate settlement amount	0	0
Maximum [Member]
Commitments And Contingencies [Line Items]
Aggregate settlement amount	250	250
Anthem, Inc. v. Express Scripts, Inc. [Member]
Commitments And Contingencies [Line Items]
Proceeds originally received at time of divestiture	4,675	4,675
Anthem, Inc. v. Express Scripts, Inc. [Member] | Damages for Pharmacy Pricing [Member]
Commitments And Contingencies [Line Items]
Approximate amount of damages sought for breaches	14,800	14,800
Anthem, Inc. v. Express Scripts, Inc. [Member] | Damages for Operational Breaches [Member]
Commitments And Contingencies [Line Items]
Approximate amount of damages sought for breaches	158	$ 158
BCBS Antitrust Litigation [Member]
Commitments And Contingencies [Line Items]
Aggregate settlement amount	596
Loss Contingency Accrual, Payments	$ 506