Significant Accounting Policies - Disaggregation of Revenue (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Disaggregation of Revenue [Line Items]
Revenues	$ 290,912	$ 267,908	$ 255,765
Net investment income	1,199	798	1,011
Total revenues	292,111	268,706	256,776
Pharmacy
Disaggregation of Revenue [Line Items]
Revenues	184,618	171,289	165,925
Front Store
Disaggregation of Revenue [Line Items]
Revenues	21,315	19,655	19,422
Premiums
Disaggregation of Revenue [Line Items]
Revenues	76,132	69,364	63,122
Other
Disaggregation of Revenue [Line Items]
Revenues	8,847	7,600	7,296
Operating Segments | Health Care Benefits
Disaggregation of Revenue [Line Items]
Revenues	81,515	74,926	68,979
Net investment income	586	483	599
Total revenues	82,186	75,467	69,604
Operating Segments | Health Care Benefits | Pharmacy
Disaggregation of Revenue [Line Items]
Revenues	0	0	0
Operating Segments | Health Care Benefits | Front Store
Disaggregation of Revenue [Line Items]
Revenues	0	0	0
Operating Segments | Health Care Benefits | Premiums
Disaggregation of Revenue [Line Items]
Revenues	76,064	69,301	63,031
Operating Segments | Health Care Benefits | Other
Disaggregation of Revenue [Line Items]
Revenues	5,536	5,683	5,974
Operating Segments | Pharmacy Services
Disaggregation of Revenue [Line Items]
Revenues	143,194	132,663	130,428
Net investment income	0	0	0
Total revenues	153,022	141,938	141,491
Operating Segments | Pharmacy Services | Pharmacy network
Disaggregation of Revenue [Line Items]
Total revenues	91,715	85,045	88,755
Operating Segments | Pharmacy Services | Mail choice
Disaggregation of Revenue [Line Items]
Total revenues	60,547	56,071	52,141
Operating Segments | Pharmacy Services | Other
Disaggregation of Revenue [Line Items]
Total revenues	760	822	595
Operating Segments | Pharmacy Services | Pharmacy
Disaggregation of Revenue [Line Items]
Revenues	152,262	141,116	140,896
Operating Segments | Pharmacy Services | Front Store
Disaggregation of Revenue [Line Items]
Revenues	0	0	0
Operating Segments | Pharmacy Services | Premiums
Disaggregation of Revenue [Line Items]
Revenues	0	0	0
Operating Segments | Pharmacy Services | Other
Disaggregation of Revenue [Line Items]
Revenues	760	822	595
Operating Segments | Retail/ LTC
Disaggregation of Revenue [Line Items]
Revenues	66,078	60,208	56,258
Net investment income	17	0	0
Total revenues	100,105	91,198	86,608
Operating Segments | Retail/ LTC | Pharmacy
Disaggregation of Revenue [Line Items]
Revenues	76,121	70,176	66,442
Operating Segments | Retail/ LTC | Front Store
Disaggregation of Revenue [Line Items]
Revenues	21,315	19,655	19,422
Operating Segments | Retail/ LTC | Premiums
Disaggregation of Revenue [Line Items]
Revenues	0	0	0
Operating Segments | Retail/ LTC | Other
Disaggregation of Revenue [Line Items]
Revenues	2,652	1,367	744
Corporate/ Other
Disaggregation of Revenue [Line Items]
Revenues	125	111	100
Net investment income	596	315	412
Total revenues	721	426	512
Corporate/ Other | Pharmacy
Disaggregation of Revenue [Line Items]
Revenues	0	0	0
Corporate/ Other | Front Store
Disaggregation of Revenue [Line Items]
Revenues	0	0	0
Corporate/ Other | Premiums
Disaggregation of Revenue [Line Items]
Revenues	68	63	91
Corporate/ Other | Other
Disaggregation of Revenue [Line Items]
Revenues	57	48	9
Intersegment Eliminations
Disaggregation of Revenue [Line Items]
Net investment income	0	0	0
Total revenues	(43,923)	(40,323)	(41,439)
Intersegment Eliminations | Pharmacy
Disaggregation of Revenue [Line Items]
Revenues	(43,765)	(40,003)	(41,413)
Intersegment Eliminations | Front Store
Disaggregation of Revenue [Line Items]
Revenues	0	0	0
Intersegment Eliminations | Premiums
Disaggregation of Revenue [Line Items]
Revenues	0	0	0
Intersegment Eliminations | Other
Disaggregation of Revenue [Line Items]
Revenues	$ (158)	$ (320)	$ (26)