Goodwill And Other Intangible Assets (Components Of Other Intangible Assets) (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Intangible Assets [Line Items]
Gross Carrying Amount, Finite Lived Intangibles	$ 3,550.8	$ 3,636.0
Accumulated Amortization, Finite Lived Intangibles	(2,876.2)	(2,768.3)
Net Carrying Amount, Finite Lived Intangibles	674.6	867.7
Gross Carrying Amount, Indefinite Lived Intangibles	7,290.3	7,290.3
Net Carrying Amount, Indefinite Lived Intangibles	7,290.3	7,290.3
Gross Carrying Amount, Total Intangible Assets	10,841.1	10,926.3
Accumulated Amortization, Total Intangible Assets	(2,876.2)	(2,768.3)
Net Carrying Amount, Total Intangible Assets	7,964.9	8,158.0
Blue Cross And Blue Shield And Other Trademarks [Member]
Intangible Assets [Line Items]
Gross Carrying Amount, Indefinite Lived Intangibles	6,298.7	6,298.7
Net Carrying Amount, Indefinite Lived Intangibles	6,298.7	6,298.7
State Medicaid Licenses [Member]
Intangible Assets [Line Items]
Gross Carrying Amount, Indefinite Lived Intangibles	991.6	991.6
Net Carrying Amount, Indefinite Lived Intangibles	991.6	991.6
Customer Relationships [Member]
Intangible Assets [Line Items]
Gross Carrying Amount, Finite Lived Intangibles	3,310.9	3,394.4
Accumulated Amortization, Finite Lived Intangibles	(2,759.7)	(2,670.0)
Net Carrying Amount, Finite Lived Intangibles	551.2	724.4
Provider And Hospital Relationships [Member]
Intangible Assets [Line Items]
Gross Carrying Amount, Finite Lived Intangibles	150.5	150.9
Accumulated Amortization, Finite Lived Intangibles	(65.9)	(58.6)
Net Carrying Amount, Finite Lived Intangibles	84.6	92.3
Other [Member]
Intangible Assets [Line Items]
Gross Carrying Amount, Finite Lived Intangibles	89.4	90.7
Accumulated Amortization, Finite Lived Intangibles	(50.6)	(39.7)
Net Carrying Amount, Finite Lived Intangibles	$ 38.8	$ 51.0