Segment Information (Financial Data By Reportable Segment) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Segment Reporting Information [Line Items]
Reportable segments operating revenues	$ 29,178	$ 25,177	$ 58,626	$ 49,565
Operating gain (loss)	3,360	1,433	5,554	3,373
Commercial & Specialty [Member]
Segment Reporting Information [Line Items]
Operating gain (loss)	1,372	983	2,792	2,581
Government Business [Member]
Segment Reporting Information [Line Items]
Operating gain (loss)	1,618	480	2,029	854
IngenioRx Segment [Member]
Segment Reporting Information [Line Items]
Operating gain (loss)	304	0	653	0
Other [Member]
Segment Reporting Information [Line Items]
Operating gain (loss)	66	(30)	80	(62)
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Reportable segments operating revenues	(3,574)	(572)	(7,177)	(1,050)
Unaffiliated
Segment Reporting Information [Line Items]
Reportable segments operating revenues	29,178	25,177	58,626	49,565
Unaffiliated | Commercial & Specialty [Member]
Segment Reporting Information [Line Items]
Reportable segments operating revenues	8,789	9,417	18,150	18,809
Unaffiliated | Government Business [Member]
Segment Reporting Information [Line Items]
Reportable segments operating revenues	17,242	15,538	34,708	30,464
Unaffiliated | IngenioRx Segment [Member]
Segment Reporting Information [Line Items]
Reportable segments operating revenues	2,544	145	4,887	145
Unaffiliated | Other [Member]
Segment Reporting Information [Line Items]
Reportable segments operating revenues	603	77	881	147
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	2,725	103	5,579	103
Affiliated [Member] | Other [Member]
Segment Reporting Information [Line Items]
Reportable segments operating revenues	$ 849	$ 469	$ 1,598	$ 947