Segment Information (Financial Data By Reportable Segment) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Segment Reporting Information [Line Items]
Reportable segments operating revenues	$ 29,448	$ 24,388
Operating gain (loss)	2,194	1,940
Commercial & Specialty [Member]
Segment Reporting Information [Line Items]
Operating gain (loss)	1,420	1,598
Government Business [Member]
Segment Reporting Information [Line Items]
Operating gain (loss)	411	374
IngenioRx Segment [Member]
Segment Reporting Information [Line Items]
Operating gain (loss)	349	0
Other [Member]
Segment Reporting Information [Line Items]
Operating gain (loss)	14	(32)
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Reportable segments operating revenues	(3,603)	(477)
Unaffiliated
Segment Reporting Information [Line Items]
Reportable segments operating revenues	29,448	24,388
Unaffiliated | Commercial & Specialty [Member]
Segment Reporting Information [Line Items]
Reportable segments operating revenues	9,361	9,392
Unaffiliated | Government Business [Member]
Segment Reporting Information [Line Items]
Reportable segments operating revenues	17,466	14,925
Unaffiliated | IngenioRx Segment [Member]
Segment Reporting Information [Line Items]
Reportable segments operating revenues	2,344	0
Unaffiliated | Other [Member]
Segment Reporting Information [Line Items]
Reportable segments operating revenues	277	71
Affiliated [Member]
Segment Reporting Information [Line Items]
Reportable segments operating revenues	0	0
Affiliated [Member] | Commercial & Specialty [Member]
Segment Reporting Information [Line Items]
Reportable segments operating revenues	0	0
Affiliated [Member] | Government Business [Member]
Segment Reporting Information [Line Items]
Reportable segments operating revenues	0	0
Affiliated [Member] | IngenioRx Segment [Member]
Segment Reporting Information [Line Items]
Reportable segments operating revenues	2,853	0
Affiliated [Member] | Other [Member]
Segment Reporting Information [Line Items]
Reportable segments operating revenues	$ 750	$ 477