Segment Information (Major Product Revenues) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Major Product Revenue By Segment [Line Items]
Insurance Services Revenue	$ 120,808	$ 103,141	$ 91,341
Commercial and Specialty Business Segment [Member]
Major Product Revenue By Segment [Line Items]
Insurance Services Revenue	36,699	37,421	35,782
Commercial and Specialty Business Segment [Member] | Managed Care Products [Member]
Major Product Revenue By Segment [Line Items]
Insurance Services Revenue	29,815	30,311	29,012
Commercial and Specialty Business Segment [Member] | Managed Care Services [Member]
Major Product Revenue By Segment [Line Items]
Insurance Services Revenue	5,296	5,451	5,218
Commercial and Specialty Business Segment [Member] | Dental Vision Products And Services [Member]
Major Product Revenue By Segment [Line Items]
Insurance Services Revenue	1,231	1,302	1,220
Commercial and Specialty Business Segment [Member] | Other Products [Member]
Major Product Revenue By Segment [Line Items]
Insurance Services Revenue	357	357	332
Government Business Segment [Member]
Major Product Revenue By Segment [Line Items]
Insurance Services Revenue	71,572	62,632	55,348
Government Business Segment [Member] | Managed Care Products [Member]
Major Product Revenue By Segment [Line Items]
Insurance Services Revenue	71,188	62,229	54,889
Government Business Segment [Member] | Managed Care Services [Member]
Major Product Revenue By Segment [Line Items]
Insurance Services Revenue	384	403	459
IngenioRx Segment [Member] | Pharmacy products and services [Member]
Major Product Revenue By Segment [Line Items]
Insurance Services Revenue	21,911	5,402	0
Other Segment [Member]
Major Product Revenue By Segment [Line Items]
Insurance Services Revenue	6,057	2,293	1,519
Other Segment [Member] | Other Products [Member]
Major Product Revenue By Segment [Line Items]
Insurance Services Revenue	270	144	30
Other Segment [Member] | Integrated health services [Member]
Major Product Revenue By Segment [Line Items]
Insurance Services Revenue	5,787	2,149	1,489
Segment Eliminations [Member]
Major Product Revenue By Segment [Line Items]
Insurance Services Revenue	$ (15,431)	$ (4,607)	$ (1,308)