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, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Medical Claims Payable [Line Items]
Gross medical claims payable, beginning of period			$ 7,992	$ 7,893
Ceded medical claims payable, beginning of period			(105)	(539)
Net medical claims payable, beginning of period			7,887	7,354
Liability For Unpaid Claims And Claims Adjustment Expense Purchase Adjustments	$ 199		199
Current period net incurred medical claims			52,576	53,505
Prior periods redundancies			(866)	(1,066)
Total net incurred medical claims	17,781	$ 17,704	51,710	52,439
Net payments attributable to current period medical claims			45,514	45,998
Net payments attributable to prior periods medical claims			6,662	5,932
Total net payments			52,176	51,930
Net medical claims payable, end of period	7,620	7,863	7,620	7,863
Ceded medical claims payable, end of period	38	101	38	101
Gross medical claims payable, end of period	7,658	7,964	7,658	7,964
Government Business Segment [Member]
Medical Claims Payable [Line Items]
Gross medical claims payable, beginning of period			4,585	4,626
Ceded medical claims payable, beginning of period			(27)	(18)
Net medical claims payable, beginning of period			4,558	4,608
Liability For Unpaid Claims And Claims Adjustment Expense Purchase Adjustments	199		199
Current period net incurred medical claims			34,537	31,634
Prior periods redundancies			(441)	(650)
Total net incurred medical claims	11,613	10,263	34,096	30,984
Net payments attributable to current period medical claims			29,993	27,274
Net payments attributable to prior periods medical claims			3,969	3,800
Total net payments			33,962	31,074
Net medical claims payable, end of period	4,891	4,518	4,891	4,518
Ceded medical claims payable, end of period	27	21	27	21
Gross medical claims payable, end of period	4,918	4,539	4,918	4,539
Commercial Specialty Business Segment [Member]
Medical Claims Payable [Line Items]
Gross medical claims payable, beginning of period			3,407	3,267
Ceded medical claims payable, beginning of period			(78)	(521)
Net medical claims payable, beginning of period			3,329	2,746
Liability For Unpaid Claims And Claims Adjustment Expense Purchase Adjustments	0		0
Current period net incurred medical claims			18,039	21,871
Prior periods redundancies			(425)	(416)
Total net incurred medical claims	6,168	7,441	17,614	21,455
Net payments attributable to current period medical claims			15,521	18,724
Net payments attributable to prior periods medical claims			2,693	2,132
Total net payments			18,214	20,856
Net medical claims payable, end of period	2,729	3,345	2,729	3,345
Ceded medical claims payable, end of period	11	80	11	80
Gross medical claims payable, end of period	$ 2,740	$ 3,425	$ 2,740	$ 3,425