DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES - Schedule of Derivative Assets and Liabilities and Locations on Consolidated Balance Sheet (Details) - Recurring - Commodity Derivative Instruments - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Derivatives, Fair Value [Line Items]
Derivative asset	$ 55	$ 24
Derivative liability	11	64
Current Assets: Prepaid assets and other
Derivatives, Fair Value [Line Items]
Derivative asset	55	8
Other Assets: Deferred charges and other
Derivatives, Fair Value [Line Items]
Derivative asset	0	16
Current Liabilities: Other current liabilities
Derivatives, Fair Value [Line Items]
Derivative liability	$ 11	$ 64