Medical Claims Payable (Reconciliation Of The Beginning And Ending Balances For Medical Claims Payable) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Medical Claims Payable [Line Items]
Gross medical claims payable, beginning of year	$ 7,814	$ 7,656	$ 7,360
Ceded medical claims payable, beginning of year	(105)	(539)	(646)
Net medical claims payable, beginning of year	7,709	7,117	6,714
Business combinations and purchase adjustments	199	76
Current Year Claims and Claims Adjustment Expense	69,581	70,377	64,868
Net incurred medical claims in prior years redundancies	(930)	(1,133)	(835)
Total net incurred medical claims	68,651	69,244	64,033
Net payments attributable to current year medical claims	62,748	62,923	57,879
Net payments attributable to prior years medical claims	6,579	5,805	5,751
Total net payments	69,327	68,728	63,630
Net medical claims payable, end of year	7,232	7,709	7,117
Ceded medical claims payable, end of year	34	105	539
Gross medical claims payable, end of year	7,266	7,814	7,656
Commercial and Specialty Business Segment [Member]
Medical Claims Payable [Line Items]
Gross medical claims payable, beginning of year	3,383	3,247	3,371
Ceded medical claims payable, beginning of year	(78)	(521)	(636)
Net medical claims payable, beginning of year	3,305	2,726	2,735
Business combinations and purchase adjustments	0	0
Current Year Claims and Claims Adjustment Expense	24,094	29,467	27,588
Net incurred medical claims in prior years redundancies	(456)	(462)	(463)
Total net incurred medical claims	23,638	29,005	27,125
Net payments attributable to current year medical claims	21,633	26,250	24,928
Net payments attributable to prior years medical claims	2,734	2,176	2,206
Total net payments	24,367	28,426	27,134
Net medical claims payable, end of year	2,576	3,305	2,726
Ceded medical claims payable, end of year	10	78	521
Gross medical claims payable, end of year	2,586	3,383	3,247
Government Business Segment [Member]
Medical Claims Payable [Line Items]
Gross medical claims payable, beginning of year	4,431	4,409	3,989
Ceded medical claims payable, beginning of year	(27)	(18)	(10)
Net medical claims payable, beginning of year	4,404	4,391	3,979
Business combinations and purchase adjustments	199	76
Current Year Claims and Claims Adjustment Expense	45,487	40,910	37,280
Net incurred medical claims in prior years redundancies	(474)	(671)	(372)
Total net incurred medical claims	45,013	40,239	36,908
Net payments attributable to current year medical claims	41,115	36,673	32,951
Net payments attributable to prior years medical claims	3,845	3,629	3,545
Total net payments	44,960	40,302	36,496
Net medical claims payable, end of year	4,656	4,404	4,391
Ceded medical claims payable, end of year	24	27	18
Gross medical claims payable, end of year	$ 4,680	$ 4,431	$ 4,409