MEDICARE PART D (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Segment Reporting Information [Line Items]
Other current assets	$ 5,276	$ 3,806
Trade accounts payable and accrued expenses	(4,013)	(3,754)
Other long-term assets	2,128	1,834
Other long-term liabilities	(1,787)	(1,141)
Risk Corridor Settlement
Segment Reporting Information [Line Items]
Other current assets	216	5
Trade accounts payable and accrued expenses	(39)	(120)
Net current asset (liability)	177	(115)
Other long-term assets	8	6
Other long-term liabilities	(90)	(61)
Net long-term liability	(82)	(55)
Total net asset (liability)	95	(170)
CMS Subsidies/ Discounts
Segment Reporting Information [Line Items]
Other current assets	1,420	585
Trade accounts payable and accrued expenses	(253)	(356)
Net current asset (liability)	1,167	229
Other long-term assets	0	0
Other long-term liabilities	0	0
Net long-term liability	0	0
Total net asset (liability)	$ 1,167	$ 229