Medical Claims Payable (Reconciliation Of The Beginning And Ending Balances For Medical Claims Payable) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Medical Claims Payable [Line Items]
Gross medical claims payable, beginning of year	$ 8,647	$ 7,266	$ 7,814
Ceded medical claims payable, beginning of year	(33)	(34)	(105)
Net medical claims payable, beginning of year	8,614	7,232	7,709
Business combinations and purchase adjustments	339		199
Current Year Claims and Claims Adjustment Expense	85,094	78,695	69,581
Net incurred medical claims in prior years redundancies	(637)	(500)	(930)
Total net incurred medical claims	84,457	78,195	68,651
Net payments attributable to current year medical claims	74,629	70,294	62,748
Net payments attributable to prior years medical claims	7,692	6,519	6,579
Total net payments	82,321	76,813	69,327
Net medical claims payable, end of year	11,089	8,614	7,232
Ceded medical claims payable, end of year	46	33	34
Gross medical claims payable, end of year	11,135	8,647	7,266
Commercial and Specialty Business Segment [Member]
Medical Claims Payable [Line Items]
Gross medical claims payable, beginning of year	3,039	2,586	3,383
Ceded medical claims payable, beginning of year	(14)	(10)	(78)
Net medical claims payable, beginning of year	3,025	2,576	3,305
Business combinations and purchase adjustments	0
Current Year Claims and Claims Adjustment Expense	24,894	25,942	24,094
Net incurred medical claims in prior years redundancies	(375)	(190)	(456)
Total net incurred medical claims	24,519	25,752	23,638
Net payments attributable to current year medical claims	21,736	23,026	21,633
Net payments attributable to prior years medical claims	2,527	2,277	2,734
Total net payments	24,263	25,303	24,367
Net medical claims payable, end of year	3,281	3,025	2,576
Ceded medical claims payable, end of year	13	14	10
Gross medical claims payable, end of year	3,294	3,039	2,586
Government Business Segment [Member]
Medical Claims Payable [Line Items]
Gross medical claims payable, beginning of year	5,608	4,680	4,431
Ceded medical claims payable, beginning of year	(19)	(24)	(27)
Net medical claims payable, beginning of year	5,589	4,656	4,404
Business combinations and purchase adjustments	141		199
Current Year Claims and Claims Adjustment Expense	58,912	52,753	45,487
Net incurred medical claims in prior years redundancies	(262)	(310)	(474)
Total net incurred medical claims	58,650	52,443	45,013
Net payments attributable to current year medical claims	51,602	47,268	41,115
Net payments attributable to prior years medical claims	5,165	4,242	3,845
Total net payments	56,767	51,510	44,960
Net medical claims payable, end of year	7,613	5,589	4,656
Ceded medical claims payable, end of year	33	19	24
Gross medical claims payable, end of year	7,646	5,608	4,680
Other Segment [Member]
Medical Claims Payable [Line Items]
Gross medical claims payable, beginning of year	0
Ceded medical claims payable, beginning of year	0
Net medical claims payable, beginning of year	0
Business combinations and purchase adjustments	198
Current Year Claims and Claims Adjustment Expense	1,288
Net incurred medical claims in prior years redundancies	0
Total net incurred medical claims	1,288	0	$ 0
Net payments attributable to current year medical claims	1,291
Net payments attributable to prior years medical claims	0
Total net payments	1,291
Net medical claims payable, end of year	195	0
Ceded medical claims payable, end of year	0	0
Gross medical claims payable, end of year	$ 195	$ 0