Segment Information Segment Information (Major Product Revenues for Each Reportable Segment) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Major Product Revenue By Segment [Line Items]
Insurance Services Revenue	$ 30,649	$ 26,444	$ 89,275	$ 76,009
Commercial Specialty Business Segment [Member]
Major Product Revenue By Segment [Line Items]
Insurance Services Revenue	9,326	9,284	27,476	28,093
Government Business Segment [Member]
Major Product Revenue By Segment [Line Items]
Insurance Services Revenue	18,101	15,955	52,809	46,419
IngenioRx Segment [Member]
Major Product Revenue By Segment [Line Items]
Insurance Services Revenue	5,582	1,922	16,048	2,170
Other Segment [Member]
Major Product Revenue By Segment [Line Items]
Insurance Services Revenue	1,798	586	4,277	1,680
Segment Eliminations [Member]
Major Product Revenue By Segment [Line Items]
Insurance Services Revenue	(4,158)	(1,303)	(11,335)	(2,353)
Managed Care Products [Member] | Commercial Specialty Business Segment [Member]
Major Product Revenue By Segment [Line Items]
Insurance Services Revenue	7,523	7,542	22,209	22,806
Managed Care Products [Member] | Government Business Segment [Member]
Major Product Revenue By Segment [Line Items]
Insurance Services Revenue	17,999	15,847	52,523	46,111
Managed Care Services [Member] | Commercial Specialty Business Segment [Member]
Major Product Revenue By Segment [Line Items]
Insurance Services Revenue	1,391	1,330	4,036	4,049
Managed Care Services [Member] | Government Business Segment [Member]
Major Product Revenue By Segment [Line Items]
Insurance Services Revenue	102	108	286	308
Dental Vision Products And Services [Member] | Commercial Specialty Business Segment [Member]
Major Product Revenue By Segment [Line Items]
Insurance Services Revenue	318	325	917	975
Other Products [Member] | Commercial Specialty Business Segment [Member]
Major Product Revenue By Segment [Line Items]
Insurance Services Revenue	94	87	314	263
Pharmacy products and services [Member] | IngenioRx Segment [Member]
Major Product Revenue By Segment [Line Items]
Insurance Services Revenue	$ 5,582	$ 1,922	$ 16,048	$ 2,170