MEDICARE PART D (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting Information [Line Items]
Other current assets	$ 3,806	$ 3,564
Trade accounts payable and accrued expenses	(3,754)	(3,067)
Other long-term assets	1,834	1,375
Other long-term liabilities	(935)	(581)
Risk Corridor Settlement
Segment Reporting Information [Line Items]
Other current assets	5	15
Trade accounts payable and accrued expenses	(120)	(103)
Net current (liability) asset	(115)	(88)
Other long-term assets	6	7
Other long-term liabilities	(61)	(89)
Net long-term liability	(55)	(82)
Total net (liability) asset	(170)	(170)
CMS Subsidies/ Discounts
Segment Reporting Information [Line Items]
Other current assets	585	172
Trade accounts payable and accrued expenses	(356)	(503)
Net current (liability) asset	229	(331)
Other long-term assets	0	0
Other long-term liabilities	0	0
Net long-term liability	0	0
Total net (liability) asset	$ 229	$ (331)