Medical Claims Payable (Reconciliation Of The Beginning And Ending Balances For Medical Claims Payable By Segment) (Details) - USD ($) $ in Millions	3 Months Ended				6 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019
Medical Claims Payable [Line Items]
Gross medical claims payable, beginning of period		$ 8,647		$ 7,266	$ 8,647	$ 7,266
Ceded medical claims payable, beginning of period		(33)		(34)	(33)	(34)
Net medical claims payable, beginning of period		8,614		7,232	8,614	7,232
Business combinations and purchase adjustments	$ 339				339
Current period net incurred medical claims					39,978	38,237
Prior periods redundancies					(700)	(414)
Total net incurred medical claims	18,748	20,530	$ 19,484	18,339	39,278	37,823
Net payments attributable to current period medical claims					31,625	30,367
Net payments attributable to prior periods medical claims					7,041	6,182
Total net payments					38,666	36,549
Short duration contract liability for unpaid claims and adjustment expense, Net	9,565		8,506		9,565	8,506
Ceded medical claims payable, end of period	90		43		90	43
Gross medical claims payable, end of period	9,655		8,549		9,655	8,549
Commercial Specialty Business Segment [Member]
Medical Claims Payable [Line Items]
Gross medical claims payable, beginning of period		3,039		2,586	3,039	2,586
Ceded medical claims payable, beginning of period		(14)		(10)	(14)	(10)
Net medical claims payable, beginning of period		3,025		2,576	3,025	2,576
Business combinations and purchase adjustments	0				0
Current period net incurred medical claims					11,318	12,460
Prior periods redundancies					(374)	(182)
Total net incurred medical claims	5,147	5,797	6,422	5,856	10,944	12,278
Net payments attributable to current period medical claims					9,014	9,928
Net payments attributable to prior periods medical claims					2,218	2,081
Total net payments					11,232	12,009
Short duration contract liability for unpaid claims and adjustment expense, Net	2,737		2,845		2,737	2,845
Ceded medical claims payable, end of period	62		14		62	14
Gross medical claims payable, end of period	2,799		2,859		2,799	2,859
Government Business Segment [Member]
Medical Claims Payable [Line Items]
Gross medical claims payable, beginning of period		5,608		4,680	5,608	4,680
Ceded medical claims payable, beginning of period		(19)		(24)	(19)	(24)
Net medical claims payable, beginning of period		5,589		4,656	5,589	4,656
Business combinations and purchase adjustments	141				141
Current period net incurred medical claims					28,162	25,777
Prior periods redundancies					(326)	(232)
Total net incurred medical claims	13,233	14,603	13,062	12,483	27,836	25,545
Net payments attributable to current period medical claims					22,115	20,439
Net payments attributable to prior periods medical claims					4,823	4,101
Total net payments					26,938	24,540
Short duration contract liability for unpaid claims and adjustment expense, Net	6,628		5,661		6,628	5,661
Ceded medical claims payable, end of period	28		29		28	29
Gross medical claims payable, end of period	6,656		5,690		6,656	5,690
Other Segment [Member]
Medical Claims Payable [Line Items]
Gross medical claims payable, beginning of period		0		0	0	0
Ceded medical claims payable, beginning of period		0		0	0	0
Net medical claims payable, beginning of period		0		$ 0	0	0
Business combinations and purchase adjustments	198				198
Current period net incurred medical claims					498	0
Prior periods redundancies					0	0
Total net incurred medical claims	368	$ 130			498	0
Net payments attributable to current period medical claims					496	0
Net payments attributable to prior periods medical claims					0	0
Total net payments					496	0
Short duration contract liability for unpaid claims and adjustment expense, Net	200		0		200	0
Ceded medical claims payable, end of period	0		0		0	0
Gross medical claims payable, end of period	$ 200		$ 0		$ 200	$ 0