Goodwill And Other Intangible Assets (Components Of Other Intangible Assets) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Intangible Assets [Line Items]
Gross Carrying Amount, Finite Lived Intangibles	$ 5,947	$ 5,080
Accumulated Amortization, Finite Lived Intangibles	(4,057)	(3,696)
Net Carrying Amount, Finite Lived Intangibles	1,890	1,384
Gross Carrying Amount, Indefinite Lived Intangibles	7,515	7,290
Net Carrying Amount, Indefinite Lived Intangibles	7,515	7,290
Gross Carrying Amount, Total Intangible Assets	13,462	12,370
Accumulated Amortization, Total Intangible Assets	(4,057)	(3,696)
Net Carrying Amount, Total Intangible Assets	9,405	8,674
Blue Cross And Blue Shield And Other Trademarks [Member]
Intangible Assets [Line Items]
Gross Carrying Amount, Indefinite Lived Intangibles	6,299	6,299
Net Carrying Amount, Indefinite Lived Intangibles	6,299	6,299
State Medicaid Licenses [Member]
Intangible Assets [Line Items]
Gross Carrying Amount, Indefinite Lived Intangibles	1,216	991
Net Carrying Amount, Indefinite Lived Intangibles	1,216	991
Customer Relationships [Member]
Intangible Assets [Line Items]
Gross Carrying Amount, Finite Lived Intangibles	5,180	4,500
Accumulated Amortization, Finite Lived Intangibles	(3,766)	(3,469)
Net Carrying Amount, Finite Lived Intangibles	1,414	1,031
Provider And Hospital Relationships [Member]
Intangible Assets [Line Items]
Gross Carrying Amount, Finite Lived Intangibles	323	228
Accumulated Amortization, Finite Lived Intangibles	(114)	(98)
Net Carrying Amount, Finite Lived Intangibles	209	130
Other [Member]
Intangible Assets [Line Items]
Gross Carrying Amount, Finite Lived Intangibles	444	352
Accumulated Amortization, Finite Lived Intangibles	(177)	(129)
Net Carrying Amount, Finite Lived Intangibles	$ 267	$ 223