Medical Claims Payable (Reconciliation Of Net Incurred Medical Claims To Benefit Expense) (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
Reconciliation of net incurred medical claims to benefit expense [Line Items]
Total net incurred medical claims	$ 21,999	$ 18,748	$ 20,530	$ 19,897	$ 19,484	$ 18,339	$ 61,277	$ 57,720
Quality improvement and other claims expense	922	799	959	856	884	943	2,680	2,683
Benefit expense	22,921	19,547	21,489	20,753	20,368	19,282	63,957	60,403
Commercial Specialty Business Segment [Member]
Reconciliation of net incurred medical claims to benefit expense [Line Items]
Total net incurred medical claims	6,641	5,147	5,797	6,546	6,422	5,856	17,585	18,824
Government Business Segment [Member]
Reconciliation of net incurred medical claims to benefit expense [Line Items]
Total net incurred medical claims	14,978	13,233	14,603	$ 13,351	$ 13,062	$ 12,483	42,814	38,896
Other Segment [Member]
Reconciliation of net incurred medical claims to benefit expense [Line Items]
Total net incurred medical claims	$ 380	$ 368	$ 130				$ 878	$ 0