Segment Information Segment Information (Major Product Revenues for Each Reportable Segment) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Major Product Revenue By Segment [Line Items]
Insurance Services Revenue	$ 29,448	$ 24,388
Commercial Specialty Business Segment [Member]
Major Product Revenue By Segment [Line Items]
Insurance Services Revenue	9,361	9,392
Government Business Segment [Member]
Major Product Revenue By Segment [Line Items]
Insurance Services Revenue	17,466	14,925
IngenioRx Segment [Member]
Major Product Revenue By Segment [Line Items]
Insurance Services Revenue	5,197	0
Other Segment [Member]
Major Product Revenue By Segment [Line Items]
Insurance Services Revenue	1,027	548
Segment Eliminations [Member]
Major Product Revenue By Segment [Line Items]
Insurance Services Revenue	(3,603)	(477)
Managed Care Products [Member] | Commercial Specialty Business Segment [Member]
Major Product Revenue By Segment [Line Items]
Insurance Services Revenue	7,569	7,618
Managed Care Products [Member] | Government Business Segment [Member]
Major Product Revenue By Segment [Line Items]
Insurance Services Revenue	17,375	14,821
Managed Care Services [Member] | Commercial Specialty Business Segment [Member]
Major Product Revenue By Segment [Line Items]
Insurance Services Revenue	1,381	1,366
Managed Care Services [Member] | Government Business Segment [Member]
Major Product Revenue By Segment [Line Items]
Insurance Services Revenue	91	104
Dental Vision Products And Services [Member] | Commercial Specialty Business Segment [Member]
Major Product Revenue By Segment [Line Items]
Insurance Services Revenue	315	323
Other Products [Member] | Commercial Specialty Business Segment [Member]
Major Product Revenue By Segment [Line Items]
Insurance Services Revenue	96	85
Pharmacy products and services [Member] | IngenioRx Segment [Member]
Major Product Revenue By Segment [Line Items]
Insurance Services Revenue	$ 5,197	$ 0