Segment Information (Financial Data By Reportable Segment) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting Information [Line Items]
Reportable segments operating revenues	$ 120,808	$ 103,141	$ 91,341
Operating gain (loss)	6,360	5,999	5,426
Depreciation and amortization of property and equipment	638	675	652
Commercial and Specialty Business Segment [Member]
Segment Reporting Information [Line Items]
Reportable segments operating revenues	36,699	37,421	35,782
Government Business Segment [Member]
Segment Reporting Information [Line Items]
Reportable segments operating revenues	71,572	62,632	55,348
Other [Member]
Segment Reporting Information [Line Items]
Reportable segments operating revenues	6,057	2,293	1,519
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Reportable segments operating revenues	(15,431)	(4,607)	(1,308)
Affiliated [Member] | Other [Member]
Segment Reporting Information [Line Items]
Reportable segments operating revenues	3,904	1,212	1,308
Affiliated [Member] | IngenioRx Segment [Member]
Segment Reporting Information [Line Items]
Reportable segments operating revenues	11,527	3,395
Commercial and Specialty Business Segment [Member]
Segment Reporting Information [Line Items]
Reportable segments operating revenues	36,699	37,421	35,782
Operating gain (loss)	2,681	4,032	3,600
Depreciation and amortization of property and equipment	0	0	0
Government Business Segment [Member]
Segment Reporting Information [Line Items]
Reportable segments operating revenues	71,572	62,632	55,348
Operating gain (loss)	2,444	2,056	1,928
Depreciation and amortization of property and equipment	0	0	0
Other [Member]
Segment Reporting Information [Line Items]
Operating gain (loss)	(126)	(89)	(102)
Depreciation and amortization of property and equipment	638	675	652
Other [Member] | Unaffiliated [Member]
Segment Reporting Information [Line Items]
Reportable segments operating revenues	2,153	1,081	$ 211
IngenioRx Segment [Member]
Segment Reporting Information [Line Items]
Operating gain (loss)	1,361
IngenioRx Segment [Member] | Unaffiliated [Member]
Segment Reporting Information [Line Items]
Reportable segments operating revenues	$ 10,384	$ 2,007