SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Health Care Cost Payments, Net (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Accounting Policies [Abstract]
Health care cost payments	$ (7,073)	$ (7,110)	$ (6,943)
Health care cost reimbursements	7,130	7,135	6,898
Net reimbursements (payments)	$ 57	$ 25	$ (45)