FAIR VALUE MEASUREMENTS AND FINANCIAL INSTRUMENTS - Assets and Liabilities Measured on a Non-Recurring Basis and Fair Value of Long-term Debt, Narrative (Details) - Nonrecurring adjustment - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Non-current assets held for sale	$ 186	$ 245
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Non-current assets held for sale	0	0
Fair value of long-term debt	$ 24,877	$ 25,378