Goodwill, Other Intangibles and Property and Equipment - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Schedule Of Goodwill, Other Intangible Assets And Property, Plant And Equipment [Line Items]
Goodwill	$ 44,648	$ 44,602	$ 44,505
Impairments of other intangible assets
Indefinite-lived intangible assets	$ 8,500	$ 8,400
Minimum
Schedule Of Goodwill, Other Intangible Assets And Property, Plant And Equipment [Line Items]
Amortization period	3 years
Maximum
Schedule Of Goodwill, Other Intangible Assets And Property, Plant And Equipment [Line Items]
Amortization period	39 years
Buildings and Improvements | Minimum
Schedule Of Goodwill, Other Intangible Assets And Property, Plant And Equipment [Line Items]
Estimated useful life	10 years
Buildings and Improvements | Maximum
Schedule Of Goodwill, Other Intangible Assets And Property, Plant And Equipment [Line Items]
Estimated useful life	40 years
Purchased Software | Minimum
Schedule Of Goodwill, Other Intangible Assets And Property, Plant And Equipment [Line Items]
Estimated useful life	3 years
Purchased Software | Maximum
Schedule Of Goodwill, Other Intangible Assets And Property, Plant And Equipment [Line Items]
Estimated useful life	5 years
Internally-Developed Software | Minimum
Schedule Of Goodwill, Other Intangible Assets And Property, Plant And Equipment [Line Items]
Estimated useful life	3 years
Internally-Developed Software | Maximum
Schedule Of Goodwill, Other Intangible Assets And Property, Plant And Equipment [Line Items]
Estimated useful life	7 years
Furniture and Equipment (including Computer Equipment) | Minimum
Schedule Of Goodwill, Other Intangible Assets And Property, Plant And Equipment [Line Items]
Estimated useful life	3 years
Furniture and Equipment (including Computer Equipment) | Maximum
Schedule Of Goodwill, Other Intangible Assets And Property, Plant And Equipment [Line Items]
Estimated useful life	10 years
Evernorth
Schedule Of Goodwill, Other Intangible Assets And Property, Plant And Equipment [Line Items]
Goodwill	$ 33,800
U.S. Medical
Schedule Of Goodwill, Other Intangible Assets And Property, Plant And Equipment [Line Items]
Goodwill	10,400
International Markets
Schedule Of Goodwill, Other Intangible Assets And Property, Plant And Equipment [Line Items]
Goodwill	$ 400