Goodwill And Other Intangible Assets (Components Of Other Intangible Assets) (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Intangible Assets [Line Items]
Gross Carrying Amount, Finite Lived Intangibles	$ 5,080	$ 5,075
Accumulated Amortization, Finite Lived Intangibles	(3,696)	(3,358)
Net Carrying Amount, Finite Lived Intangibles	1,384	1,717
Gross Carrying Amount, Indefinite Lived Intangibles	7,290	7,290
Net Carrying Amount, Indefinite Lived Intangibles	7,290	7,290
Gross Carrying Amount, Total Intangible Assets	12,370	12,365
Accumulated Amortization, Total Intangible Assets	(3,696)	(3,358)
Net Carrying Amount, Total Intangible Assets	8,674	9,007
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	991	991
Net Carrying Amount, Indefinite Lived Intangibles	991	991
Customer Relationships [Member]
Intangible Assets [Line Items]
Gross Carrying Amount, Finite Lived Intangibles	4,500	4,495
Accumulated Amortization, Finite Lived Intangibles	(3,469)	(3,185)
Net Carrying Amount, Finite Lived Intangibles	1,031	1,310
Provider And Hospital Relationships [Member]
Intangible Assets [Line Items]
Gross Carrying Amount, Finite Lived Intangibles	228	228
Accumulated Amortization, Finite Lived Intangibles	(98)	(85)
Net Carrying Amount, Finite Lived Intangibles	130	143
Other [Member]
Intangible Assets [Line Items]
Gross Carrying Amount, Finite Lived Intangibles	352	352
Accumulated Amortization, Finite Lived Intangibles	(129)	(88)
Net Carrying Amount, Finite Lived Intangibles	$ 223	$ 264