Medical Claims Payable (Reconciliation Of The Beginning And Ending Balances For Medical Claims Payable By Segment) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Medical Claims Payable [Line Items]
Gross medical claims payable, beginning of period	$ 8,647	$ 7,266
Ceded medical claims payable, beginning of period	(33)	(34)
Net medical claims payable, beginning of period	8,614	7,232
Business combinations and purchase adjustments	339
Current period net incurred medical claims	21,230	18,794
Prior periods redundancies	(700)	(455)
Total net incurred medical claims	20,530	18,339
Net payments attributable to current period medical claims	13,744	12,163
Net payments attributable to prior periods medical claims	6,109	5,414
Total net payments	19,853	17,577
Short duration contract liability for unpaid claims and adjustment expense, Net	9,630	7,994
Ceded medical claims payable, end of period	60	34
Gross medical claims payable, end of period	9,690	8,028
Commercial Specialty Business Segment [Member]
Medical Claims Payable [Line Items]
Gross medical claims payable, beginning of period	3,039	2,586
Ceded medical claims payable, beginning of period	(14)	(10)
Net medical claims payable, beginning of period	3,025	2,576
Business combinations and purchase adjustments	0
Current period net incurred medical claims	6,090	6,053
Prior periods redundancies	(293)	(197)
Total net incurred medical claims	5,797	5,856
Net payments attributable to current period medical claims	3,908	3,898
Net payments attributable to prior periods medical claims	1,875	1,766
Total net payments	5,783	5,664
Short duration contract liability for unpaid claims and adjustment expense, Net	3,039	2,768
Ceded medical claims payable, end of period	37	8
Gross medical claims payable, end of period	3,076	2,776
Government Business Segment [Member]
Medical Claims Payable [Line Items]
Gross medical claims payable, beginning of period	5,608	4,680
Ceded medical claims payable, beginning of period	(19)	(24)
Net medical claims payable, beginning of period	5,589	4,656
Business combinations and purchase adjustments	141
Current period net incurred medical claims	15,010	12,741
Prior periods redundancies	(407)	(258)
Total net incurred medical claims	14,603	12,483
Net payments attributable to current period medical claims	9,698	8,265
Net payments attributable to prior periods medical claims	4,234	3,648
Total net payments	13,932	11,913
Short duration contract liability for unpaid claims and adjustment expense, Net	6,401	5,226
Ceded medical claims payable, end of period	23	26
Gross medical claims payable, end of period	6,424	5,252
Other Segment [Member]
Medical Claims Payable [Line Items]
Gross medical claims payable, beginning of period	0	0
Ceded medical claims payable, beginning of period	0	0
Net medical claims payable, beginning of period	0	0
Business combinations and purchase adjustments	198
Current period net incurred medical claims	130	0
Prior periods redundancies	0	0
Total net incurred medical claims	130	0
Net payments attributable to current period medical claims	138	0
Net payments attributable to prior periods medical claims	0	0
Total net payments	138	0
Short duration contract liability for unpaid claims and adjustment expense, Net	190	0
Ceded medical claims payable, end of period	0	0
Gross medical claims payable, end of period	$ 190	$ 0