Segment Reporting - Reconciliation of Financial Measures of Segments to Consolidated Totals (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Revenue, Major Customer [Line Items]
Revenues from external customers	$ 73,548	$ 66,852	$ 214,675	$ 198,602
Net investment income (loss)	246	204	832	550
Total revenues	73,794	67,056	215,507	199,152
Adjusted operating income (loss)	4,073	3,622	13,165	13,063
Health Care Benefits
Revenue, Major Customer [Line Items]
Total revenues	20,479	18,698	61,487	56,364
Pharmacy Services
Revenue, Major Customer [Line Items]
Total revenues	39,046	35,711	113,681	105,583
Retail/ LTC
Revenue, Major Customer [Line Items]
Total revenues	24,992	22,725	72,994	67,136
Operating Segments | Health Care Benefits
Revenue, Major Customer [Line Items]
Revenues from external customers	20,311	18,557	60,993	55,972
Net investment income (loss)	147	121	432	341
Total revenues	20,479	18,698	61,487	56,364
Adjusted operating income (loss)	1,106	1,080	4,502	6,035
Operating Segments | Pharmacy Services
Revenue, Major Customer [Line Items]
Revenues from external customers	36,851	33,492	105,909	98,233
Net investment income (loss)	0	0	0	0
Total revenues	39,046	35,711	113,681	105,583
Adjusted operating income (loss)	1,773	1,619	5,035	4,127
Copayments	2,800	2,500	9,000	8,500
Operating Segments | Retail/ LTC
Revenue, Major Customer [Line Items]
Revenues from external customers	16,347	14,770	47,672	44,314
Net investment income (loss)	(33)	0	13	0
Total revenues	24,992	22,725	72,994	67,136
Adjusted operating income (loss)	1,723	1,412	5,166	4,371
Intersegment Eliminations
Revenue, Major Customer [Line Items]
Revenues	(10,894)	(10,194)	(33,143)	(30,223)
Net investment income (loss)	0	0	0	0
Total revenues	(10,894)	(10,194)	(33,143)	(30,223)
Adjusted operating income (loss)	(186)	(186)	(523)	(539)
Intersegment Eliminations | Health Care Benefits
Revenue, Major Customer [Line Items]
Revenues	21	20	62	51
Intersegment Eliminations | Pharmacy Services
Revenue, Major Customer [Line Items]
Revenues	2,195	2,219	7,772	7,350
Intersegment Eliminations | Retail/ LTC
Revenue, Major Customer [Line Items]
Revenues	8,678	7,955	25,309	22,822
Corporate/ Other
Revenue, Major Customer [Line Items]
Revenues from external customers	39	33	101	83
Net investment income (loss)	132	83	387	209
Total revenues	171	116	488	292
Adjusted operating income (loss)	$ (343)	$ (303)	$ (1,015)	$ (931)