Medical Claims Payable (Reconciliation Of The Beginning And Ending Balances For Medical Claims Payable) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Medical Claims Payable [Line Items]
Gross medical claims payable, beginning of year	$ 7,266	$ 7,814	$ 7,656
Ceded medical claims payable, beginning of year	(34)	(105)	(539)
Net medical claims payable, beginning of year	7,232	7,709	7,117
Business combinations and purchase adjustments		199	76
Current Year Claims and Claims Adjustment Expense	78,695	69,581	70,377
Net incurred medical claims in prior years redundancies	(500)	(930)	(1,133)
Total net incurred medical claims	78,195	68,651	69,244
Net payments attributable to current year medical claims	70,294	62,748	62,923
Net payments attributable to prior years medical claims	6,519	6,579	5,805
Total net payments	76,813	69,327	68,728
Net medical claims payable, end of year	8,614	7,232	7,709
Ceded medical claims payable, end of year	33	34	105
Gross medical claims payable, end of year	8,647	7,266	7,814
Commercial and Specialty Business Segment [Member]
Medical Claims Payable [Line Items]
Gross medical claims payable, beginning of year	2,586	3,383	3,247
Ceded medical claims payable, beginning of year	(10)	(78)	(521)
Net medical claims payable, beginning of year	2,576	3,305	2,726
Current Year Claims and Claims Adjustment Expense	25,942	24,094	29,467
Net incurred medical claims in prior years redundancies	(190)	(456)	(462)
Total net incurred medical claims	25,752	23,638	29,005
Net payments attributable to current year medical claims	23,026	21,633	26,250
Net payments attributable to prior years medical claims	2,277	2,734	2,176
Total net payments	25,303	24,367	28,426
Net medical claims payable, end of year	3,025	2,576	3,305
Ceded medical claims payable, end of year	14	10	78
Gross medical claims payable, end of year	3,039	2,586	3,383
Government Business Segment [Member]
Medical Claims Payable [Line Items]
Gross medical claims payable, beginning of year	4,680	4,431	4,409
Ceded medical claims payable, beginning of year	(24)	(27)	(18)
Net medical claims payable, beginning of year	4,656	4,404	4,391
Business combinations and purchase adjustments		199	76
Current Year Claims and Claims Adjustment Expense	52,753	45,487	40,910
Net incurred medical claims in prior years redundancies	(310)	(474)	(671)
Total net incurred medical claims	52,443	45,013	40,239
Net payments attributable to current year medical claims	47,268	41,115	36,673
Net payments attributable to prior years medical claims	4,242	3,845	3,629
Total net payments	51,510	44,960	40,302
Net medical claims payable, end of year	5,589	4,656	4,404
Ceded medical claims payable, end of year	19	24	27
Gross medical claims payable, end of year	$ 5,608	$ 4,680	$ 4,431