Medical Claims Payable (Incurred and Paid Claims Development, Net of Reinsurance) (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Claims Development [Line Items]
Cumulative incurred claims and allocated claim adjustment expenses, net of reinsurance	$ 305,246
Cumulative paid claims and allocated claim adjustment expenses, net of reinsurance	289,904
Commercial and Specialty Business [Member]
Claims Development [Line Items]
Cumulative incurred claims and allocated claim adjustment expenses, net of reinsurance	85,128
Cumulative paid claims and allocated claim adjustment expenses, net of reinsurance	81,014
Commercial and Specialty Business [Member] | Short-duration Insurance Contracts, Claim Year 2020 and Prior [Member]
Claims Development [Line Items]
Cumulative incurred claims and allocated claim adjustment expenses, net of reinsurance	27,101	$ 27,080	$ 27,545
Cumulative paid claims and allocated claim adjustment expenses, net of reinsurance	27,049	26,876	24,263
Commercial and Specialty Business [Member] | Short-duration Insurance Contracts, Claim Year 2021 [Member]
Claims Development [Line Items]
Cumulative incurred claims and allocated claim adjustment expenses, net of reinsurance	27,957	28,132
Cumulative paid claims and allocated claim adjustment expenses, net of reinsurance	27,691	24,502
Commercial and Specialty Business [Member] | Short-Duration Insurance Contract, Claim Year 2022 [Member]
Claims Development [Line Items]
Cumulative incurred claims and allocated claim adjustment expenses, net of reinsurance	30,070
Cumulative paid claims and allocated claim adjustment expenses, net of reinsurance	26,274
Government Business Segment [Member]
Claims Development [Line Items]
Cumulative incurred claims and allocated claim adjustment expenses, net of reinsurance	215,498
Cumulative paid claims and allocated claim adjustment expenses, net of reinsurance	204,569
Government Business Segment [Member] | Short-duration Insurance Contracts, Claim Year 2020 and Prior [Member]
Claims Development [Line Items]
Cumulative incurred claims and allocated claim adjustment expenses, net of reinsurance	63,123	63,158	64,379
Cumulative paid claims and allocated claim adjustment expenses, net of reinsurance	62,981	62,821	56,767
Government Business Segment [Member] | Short-duration Insurance Contracts, Claim Year 2021 [Member]
Claims Development [Line Items]
Cumulative incurred claims and allocated claim adjustment expenses, net of reinsurance	70,450	71,045
Cumulative paid claims and allocated claim adjustment expenses, net of reinsurance	70,125	62,233
Government Business Segment [Member] | Short-Duration Insurance Contract, Claim Year 2022 [Member]
Claims Development [Line Items]
Cumulative incurred claims and allocated claim adjustment expenses, net of reinsurance	81,925
Cumulative paid claims and allocated claim adjustment expenses, net of reinsurance	71,463
Other Segment [Member]
Claims Development [Line Items]
Cumulative incurred claims and allocated claim adjustment expenses, net of reinsurance	4,620
Cumulative paid claims and allocated claim adjustment expenses, net of reinsurance	4,321
Other Segment [Member] | Short-duration Insurance Contracts, Claim Year 2020 and Prior [Member]
Claims Development [Line Items]
Cumulative incurred claims and allocated claim adjustment expenses, net of reinsurance	1,459	1,470	1,486
Cumulative paid claims and allocated claim adjustment expenses, net of reinsurance	1,458	1,454	$ 1,292
Other Segment [Member] | Short-duration Insurance Contracts, Claim Year 2021 [Member]
Claims Development [Line Items]
Cumulative incurred claims and allocated claim adjustment expenses, net of reinsurance	1,609	1,683
Cumulative paid claims and allocated claim adjustment expenses, net of reinsurance	1,603	$ 1,421
Other Segment [Member] | Short-Duration Insurance Contract, Claim Year 2022 [Member]
Claims Development [Line Items]
Cumulative incurred claims and allocated claim adjustment expenses, net of reinsurance	1,552
Cumulative paid claims and allocated claim adjustment expenses, net of reinsurance	$ 1,260