SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Part D Subsidy/Discount Payments, Net (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Accounting Policies [Abstract]
Part D subsidy/discount payments	$ (16,530)	$ (14,889)	$ (13,348)
Part D subsidy/discount reimbursements	18,498	14,628	12,410
Net reimbursements (payments)	$ 1,968	$ (261)	$ (938)