MEDICARE PART D (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Segment Reporting Information [Line Items]
Other current assets	$ 6,202	$ 5,276
Trade accounts payable and accrued expenses	(4,777)	(4,013)
Other long-term assets	2,455	2,128
Other long-term liabilities	(1,863)	(1,787)
Risk Corridor Settlement
Segment Reporting Information [Line Items]
Other current assets	230	216
Trade accounts payable and accrued expenses	(37)	(39)
Net current asset	193	177
Other long-term assets	217	8
Other long-term liabilities	(153)	(90)
Net long-term asset (liability)	64	(82)
Total net asset	257	95
CMS Subsidies/ Discounts
Segment Reporting Information [Line Items]
Other current assets	1,670	1,420
Trade accounts payable and accrued expenses	(1,523)	(253)
Net current asset	147	1,167
Other long-term assets	0	0
Other long-term liabilities	0	0
Net long-term asset (liability)	0	0
Total net asset	$ 147	$ 1,167