MEDICARE PART D (Details) - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
Segment Reporting Information [Line Items]
Other current assets	$ 6,503	$ 5,276
Trade accounts payable and accrued expenses	(4,898)	(4,013)
Other long-term assets	2,254	2,128
Other long-term liabilities	(2,113)	(1,787)
Risk Corridor Settlement
Segment Reporting Information [Line Items]
Other current assets	169	216
Trade accounts payable and accrued expenses	(13)	(39)
Net current asset (liability)	156	177
Other long-term assets	317	8
Other long-term liabilities	(198)	(90)
Net long-term asset (liability)	119	(82)
Total net asset (liability)	275	95
CMS Subsidies/ Discounts
Segment Reporting Information [Line Items]
Other current assets	1,635	1,420
Trade accounts payable and accrued expenses	(1,653)	(253)
Net current asset (liability)	(18)	1,167
Other long-term assets	0	0
Other long-term liabilities	0	0
Net long-term asset (liability)	0	0
Total net asset (liability)	$ (18)	$ 1,167