MEDICARE PART D (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Segment Reporting Information [Line Items]
Other current assets	$ 5,170	$ 3,806
Trade accounts payable and accrued expenses	(4,472)	(3,754)
Other long-term assets	2,510	1,834
Other long-term liabilities	(1,543)	(935)
Risk Corridor Settlement
Segment Reporting Information [Line Items]
Other current assets	25	5
Trade accounts payable and accrued expenses	(101)	(120)
Net current (liability) asset	(76)	(115)
Other long-term assets	273	6
Other long-term liabilities	(176)	(61)
Net long-term asset (liability)	97	(55)
Total net asset (liability)	21	(170)
CMS Subsidies/ Discounts
Segment Reporting Information [Line Items]
Other current assets	1,226	585
Trade accounts payable and accrued expenses	(714)	(356)
Net current (liability) asset	512	229
Other long-term assets	0	0
Other long-term liabilities	0	0
Net long-term asset (liability)	0	0
Total net asset (liability)	$ 512	$ 229