Segment Information (Financial Data By Reportable Segment) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Segment Reporting Information [Line Items]
Reportable segments operating revenues	$ 33,279	$ 29,178	$ 65,377	$ 58,626
Operating gain (loss)	2,081	3,360	4,242	5,554
Commercial & Specialty [Member]
Segment Reporting Information [Line Items]
Operating gain (loss)	791	1,372	2,059	2,792
Government Business [Member]
Segment Reporting Information [Line Items]
Operating gain (loss)	868	1,618	1,346	2,029
IngenioRx Segment [Member]
Segment Reporting Information [Line Items]
Operating gain (loss)	405	304	812	653
Other [Member]
Segment Reporting Information [Line Items]
Operating gain (loss)	17	66	25	80
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Reportable segments operating revenues	(5,073)	(3,574)	(9,981)	(7,177)
Unaffiliated
Segment Reporting Information [Line Items]
Reportable segments operating revenues	33,279	29,178	65,377	58,626
Unaffiliated | Commercial & Specialty [Member]
Segment Reporting Information [Line Items]
Reportable segments operating revenues	9,550	8,789	19,041	18,150
Unaffiliated | Government Business [Member]
Segment Reporting Information [Line Items]
Reportable segments operating revenues	20,066	17,242	39,349	34,708
Unaffiliated | IngenioRx Segment [Member]
Segment Reporting Information [Line Items]
Reportable segments operating revenues	3,042	2,544	5,780	4,887
Unaffiliated | Other [Member]
Segment Reporting Information [Line Items]
Reportable segments operating revenues	621	603	1,207	881
Affiliated [Member]
Segment Reporting Information [Line Items]
Reportable segments operating revenues	0	0	0	0
Affiliated [Member] | Commercial & Specialty [Member]
Segment Reporting Information [Line Items]
Reportable segments operating revenues		0	0	0
Affiliated [Member] | Government Business [Member]
Segment Reporting Information [Line Items]
Reportable segments operating revenues		0	0	0
Affiliated [Member] | IngenioRx Segment [Member]
Segment Reporting Information [Line Items]
Reportable segments operating revenues	3,177	2,725	6,301	5,579
Affiliated [Member] | Other [Member]
Segment Reporting Information [Line Items]
Reportable segments operating revenues	$ 1,896	$ 849	$ 3,680	$ 1,598