DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES - Schedule of Derivative Assets and Liabilities Measured at Fair Value (Details) - Commodity Derivative Instruments - Recurring - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Derivative [Line Items]
Derivative asset, fair value	$ 118	$ 67
Derivative asset, netting	(70)	(43)
Derivative asset	48	24
Derivative liability, fair value	94	107
Derivative liability, netting	(70)	(43)
Derivative liability	24	64
Quoted Price in Active Markets (Level 1)
Derivative [Line Items]
Derivative asset, fair value	0	0
Derivative liability, fair value	0	0
Significant Other Inputs (Level 2)
Derivative [Line Items]
Derivative asset, fair value	118	67
Derivative liability, fair value	94	107
Significant Unobservable Inputs (Level 3)
Derivative [Line Items]
Derivative asset, fair value	0	0
Derivative liability, fair value	$ 0	$ 0