Medical Claims Payable (Reconciliation Of The Beginning And Ending Balances For Medical Claims Payable By Segment) (Details) - USD ($) $ in Millions	3 Months Ended						9 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2020	Sep. 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							61,977	58,157
Prior periods redundancies							(700)	(437)
Total net incurred medical claims	21,999	$ 18,748	20,530	$ 19,897	$ 19,484	18,339	61,277	57,720
Net payments attributable to current period medical claims							52,879	49,751
Net payments attributable to prior periods medical claims							7,489	6,466
Total net payments							60,368	56,217
Short duration contract liability for unpaid claims and adjustment expense, Net	9,862			8,735			9,862	8,735
Ceded medical claims payable, end of period	129			35			129	35
Gross medical claims payable, end of period	9,991			8,770			9,991	8,770
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							17,964	18,986
Prior periods redundancies							(379)	(162)
Total net incurred medical claims	6,641	5,147	5,797	6,546	6,422	5,856	17,585	18,824
Net payments attributable to current period medical claims							15,319	16,277
Net payments attributable to prior periods medical claims							2,426	2,213
Total net payments							17,745	18,490
Short duration contract liability for unpaid claims and adjustment expense, Net	2,865			2,910			2,865	2,910
Ceded medical claims payable, end of period	102			8			102	8
Gross medical claims payable, end of period	2,967			2,918			2,967	2,918
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							43,135	39,171
Prior periods redundancies							(321)	(275)
Total net incurred medical claims	14,978	13,233	14,603	13,351	$ 13,062	12,483	42,814	38,896
Net payments attributable to current period medical claims							36,680	33,474
Net payments attributable to prior periods medical claims							5,063	4,253
Total net payments							41,743	37,727
Short duration contract liability for unpaid claims and adjustment expense, Net	6,801			5,825			6,801	5,825
Ceded medical claims payable, end of period	27			27			27	27
Gross medical claims payable, end of period	6,828			5,852			6,828	5,852
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							878	0
Prior periods redundancies							0	0
Total net incurred medical claims	380	$ 368	$ 130				878	0
Net payments attributable to current period medical claims							880	0
Net payments attributable to prior periods medical claims							0	0
Total net payments							880	0
Short duration contract liability for unpaid claims and adjustment expense, Net	196			0			196	0
Ceded medical claims payable, end of period	0			0			0	0
Gross medical claims payable, end of period	$ 196			$ 0			$ 196	$ 0