Segment Reporting - Reconciliation from Operating Income to Adjusted Operating Income (Details)		1 Months Ended	3 Months Ended			12 Months Ended
	Jul. 31, 2020 USD ($)	Jun. 30, 2021 USD ($)	Dec. 31, 2021 USD ($) store	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Dec. 31, 2021 USD ($) store	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($) store	Aug. 31, 2019 USD ($)
Segment Reporting [Abstract]
Operating income (GAAP measure)						$ 13,193,000,000	$ 13,911,000,000	$ 11,987,000,000
Amortization of intangible assets						2,259,000,000	2,341,000,000	2,436,000,000
Acquisition-related integration costs						132,000,000	332,000,000	480,000,000
Store impairments						1,358,000,000	0	231,000,000
Goodwill impairment				$ 0	$ 0	431,000,000	0	0
Acquisition purchase price adjustments outside of measurement period						(61,000,000)	0	0
(Gain) loss on sale of subsidiaries						0	(269,000,000)	205,000,000
Receipt of fully reserved ACA risk corridor receivable						0	(307,000,000)	0
Adjusted operating income						$ 17,312,000,000	16,008,000,000	$ 15,339,000,000
Segment Reporting Information [Line Items]
Number of stores, planned closure | store						900		68
Proceeds from sale of subsidiary						$ 0	840,000,000	$ 0
U.S. Department of Health and Human Services, ACA Risk Corridor Receivables | Settled Litigation
Segment Reporting Information [Line Items]
Gain contingency, unrecorded amount							313,000,000		$ 313,000,000
Former gain contingency, recognized in current period, before tax							307,000,000
Retail/ LTC
Segment Reporting [Abstract]
Store impairments			$ 1,400,000,000			1,400,000,000
Goodwill impairment						$ 431,000,000
Segment Reporting Information [Line Items]
Number of stores, planned closure | store			900			900		68
Health Care Benefits
Segment Reporting [Abstract]
Goodwill impairment						$ 0
Segment Reporting Information [Line Items]
Receipt related purchase price adjustment from acquisition		$ 61,000,000
Coventry Health Care Workers Compensation Business | Health Care Benefits | Discontinued Operations, Disposed of by Sale
Segment Reporting [Abstract]
(Gain) loss on sale of subsidiaries							(269,000,000)
Segment Reporting Information [Line Items]
Proceeds from sale of subsidiary	$ 850,000,000						$ 850,000,000