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Business Acquisitions Business Acquisition (Assets Liabilities Acquired) (Details) individuals in Millions, $ in Millions	6 Months Ended
	Jun. 30, 2021 USD ($) states	Apr. 28, 2021 states	Dec. 31, 2020 USD ($)	Feb. 28, 2020 individuals states
Business Acquisition [Line Items]
Number of States in which Company Operates \| states	50
Goodwill	$ 24,399		$ 21,691
myNEXUS [Member]
Business Acquisition [Line Items]
Number of States in which Company Operates \| states		20
myNEXUS [Member] \| Other Segment [Member]
Business Acquisition [Line Items]
Goodwill	520
Other intangible assets	284
Beacon Health Options [Member]
Business Acquisition [Line Items]
Number of States in which Company Operates \| states				50
Number Of Lives Served \| individuals				34
Beacon Health Options [Member] \| Other Segment [Member]
Business Acquisition [Line Items]
Goodwill	1,081		$ 1,072
Goodwill, Purchase Accounting Adjustments	9
Other intangible assets	752
MMM Holdings [Member] \| Government Business Segment [Member]
Business Acquisition [Line Items]
Goodwill	2,171
Other intangible assets	$ 968
Minimum [Member] \| myNEXUS [Member] \| Other Segment [Member] \| Customer relationships and provider networks
Business Acquisition [Line Items]
Intangible assets amortization period, years	2 years
Minimum [Member] \| Beacon Health Options [Member] \| Other Segment [Member] \| Customer relationships and provider networks
Business Acquisition [Line Items]
Intangible assets amortization period, years	8 years
Maximum [Member] \| myNEXUS [Member] \| Other Segment [Member] \| Customer relationships and provider networks
Business Acquisition [Line Items]
Intangible assets amortization period, years	17 years
Maximum [Member] \| Beacon Health Options [Member] \| Other Segment [Member] \| Customer relationships and provider networks
Business Acquisition [Line Items]
Intangible assets amortization period, years	25 years