Segment Reporting - Reconciliation of Financial Measures of Segments to Consolidated Totals (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Revenue, Major Customer [Line Items]
Revenues from external customers	$ 72,327	$ 65,157	$ 141,127	$ 131,750
Net investment income	289	184	586	346
Total revenues	72,616	65,341	141,713	132,096
Adjusted operating income (loss)	4,887	5,328	9,092	9,441
Health Care Benefits
Revenue, Major Customer [Line Items]
Total revenues	20,525	18,468	41,008	37,666
Pharmacy Services
Revenue, Major Customer [Line Items]
Total revenues	38,314	34,889	74,635	69,872
Retail/ LTC
Revenue, Major Customer [Line Items]
Total revenues	24,728	21,662	48,002	44,411
Operating Segments | Health Care Benefits
Revenue, Major Customer [Line Items]
Revenues from external customers	20,367	18,318	40,682	37,415
Net investment income	137	127	285	220
Total revenues	20,525	18,468	41,008	37,666
Adjusted operating income (loss)	1,614	3,464	3,396	4,955
Operating Segments | Pharmacy Services
Revenue, Major Customer [Line Items]
Revenues from external customers	35,745	32,623	69,058	64,741
Net investment income	0	0	0	0
Total revenues	38,314	34,889	74,635	69,872
Adjusted operating income (loss)	1,755	1,327	3,262	2,508
Copayments	2,800	2,600	6,200	6,000
Operating Segments | Retail/ LTC
Revenue, Major Customer [Line Items]
Revenues from external customers	16,185	14,187	31,325	29,544
Net investment income	0	0	46	0
Total revenues	24,728	21,662	48,002	44,411
Adjusted operating income (loss)	2,049	1,057	3,443	2,959
Intersegment Eliminations
Revenue, Major Customer [Line Items]
Revenues	(11,133)	(9,764)	(22,249)	(20,029)
Net investment income	0	0	0	0
Total revenues	(11,133)	(9,764)	(22,249)	(20,029)
Adjusted operating income (loss)	(162)	(177)	(337)	(353)
Intersegment Eliminations | Health Care Benefits
Revenue, Major Customer [Line Items]
Revenues	21	23	41	31
Intersegment Eliminations | Pharmacy Services
Revenue, Major Customer [Line Items]
Revenues	2,569	2,266	5,577	5,131
Intersegment Eliminations | Retail/ LTC
Revenue, Major Customer [Line Items]
Revenues	8,543	7,475	16,631	14,867
Corporate/ Other
Revenue, Major Customer [Line Items]
Revenues from external customers	30	29	62	50
Net investment income	152	57	255	126
Total revenues	182	86	317	176
Adjusted operating income (loss)	$ (369)	$ (343)	$ (672)	$ (628)