Medical Claims Payable (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Claims Development [Line Items]
Net incurred medical claims in prior years redundancies	$ (869)	$ (1,703)	$ (637)
Commercial and Specialty Business Segment [Member]
Claims Development [Line Items]
Net incurred medical claims in prior years redundancies	(154)	(465)	(375)
Government Business Segment [Member]
Claims Development [Line Items]
Net incurred medical claims in prior years redundancies	(630)	(1,222)	(262)
Other Segment [Member]
Claims Development [Line Items]
Net incurred medical claims in prior years redundancies	(85)	$ (16)	$ 0
Short-duration Insurance Contracts, Claim Year 2020 and Prior [Member] | Commercial and Specialty Business Segment [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 52
Short-duration Insurance Contract, Cumulative Number of Reported Claims	80
Short-duration Insurance Contracts, Claim Year 2020 and Prior [Member] | Government Business Segment [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 142
Short-duration Insurance Contract, Cumulative Number of Reported Claims	251
Short-duration Insurance Contracts, Claim Year 2020 and Prior [Member] | Other Segment [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 1
Short-duration Insurance Contract, Cumulative Number of Reported Claims	29
Short-duration Insurance Contracts, Claim Year 2021 [Member] | Commercial and Specialty Business Segment [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 266
Short-duration Insurance Contract, Cumulative Number of Reported Claims	87
Short-duration Insurance Contracts, Claim Year 2021 [Member] | Government Business Segment [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 325
Short-duration Insurance Contract, Cumulative Number of Reported Claims	325
Short-duration Insurance Contracts, Claim Year 2021 [Member] | Other Segment [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 6
Short-duration Insurance Contract, Cumulative Number of Reported Claims	28
Short-Duration Insurance Contract, Claim Year 2022 [Member] | Commercial and Specialty Business Segment [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 3,796
Short-duration Insurance Contract, Cumulative Number of Reported Claims	81
Short-Duration Insurance Contract, Claim Year 2022 [Member] | Government Business Segment [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 10,462
Short-duration Insurance Contract, Cumulative Number of Reported Claims	298
Short-Duration Insurance Contract, Claim Year 2022 [Member] | Other Segment [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 292
Short-duration Insurance Contract, Cumulative Number of Reported Claims	25