Medical Claims Payable (Reconciliation Of Net Incurred Medical Claims To Benefit Expense) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Reconciliation of net incurred medical claims to benefit expense [Line Items]
Total net incurred medical claims	$ 20,530	$ 18,339
Quality improvement and other claims expense	959	943
Benefit expense	21,489	19,282
Commercial Specialty Business Segment [Member]
Reconciliation of net incurred medical claims to benefit expense [Line Items]
Total net incurred medical claims	5,797	5,856
Government Business Segment [Member]
Reconciliation of net incurred medical claims to benefit expense [Line Items]
Total net incurred medical claims	14,603	12,483
Other Segment [Member]
Reconciliation of net incurred medical claims to benefit expense [Line Items]
Total net incurred medical claims	$ 130	$ 0