DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES - Derivative Assets and Liabilities and Locations on Consolidated Balance Sheet (Details) - Recurring - Commodity Derivative Instruments - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Derivatives, Fair Value [Line Items]
Derivative asset	$ 11	$ 9
Derivative liability	192	103
Current Assets: Other current assets
Derivatives, Fair Value [Line Items]
Derivative asset	6	2
Noncurrent Assets: Deferred charges and other
Derivatives, Fair Value [Line Items]
Derivative asset	5	7
Deferred Credits and Other Noncurrent Liabilities: Other
Derivatives, Fair Value [Line Items]
Derivative liability	$ 192	$ 103