MEDICARE PART D (Details) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Segment Reporting Information [Line Items]
Other current assets	$ 5,631	$ 3,806
Trade accounts payable and accrued expenses	(6,175)	(3,754)
Other long-term assets	2,515	1,834
Other long-term liabilities	(1,323)	(935)
Risk Corridor Settlement
Segment Reporting Information [Line Items]
Other current assets	26	5
Trade accounts payable and accrued expenses	(100)	(120)
Net current (liability) asset	(74)	(115)
Other long-term assets	313	6
Other long-term liabilities	(149)	(61)
Net long-term asset (liability)	164	(55)
Total net asset (liability)	90	(170)
CMS Subsidies/ Discounts
Segment Reporting Information [Line Items]
Other current assets	1,010	585
Trade accounts payable and accrued expenses	(1,193)	(356)
Net current (liability) asset	(183)	229
Other long-term assets	0	0
Other long-term liabilities	0	0
Net long-term asset (liability)	0	0
Total net asset (liability)	$ (183)	$ 229