DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES - Schedule of Derivative Assets and Liabilities Measured at Fair Value (Details) - Recurring - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Derivative [Line Items]
Derivative asset	$ 1	$ 55
Derivative liability	117	11
Commodity Derivative Instruments
Derivative [Line Items]
Derivative asset, fair value	5	69
Derivative asset, netting	(4)	(14)
Derivative asset	1	55
Derivative liability, fair value	27	25
Derivative liability, netting	(4)	(14)
Derivative liability	23	11
Commodity Derivative Instruments | Quoted Price in Active Markets (Level 1)
Derivative [Line Items]
Derivative asset, fair value	0	0
Derivative liability, fair value	0	0
Commodity Derivative Instruments | Significant Other Inputs (Level 2)
Derivative [Line Items]
Derivative asset, fair value	5	69
Derivative liability, fair value	27	25
Commodity Derivative Instruments | Significant Unobservable Inputs (Level 3)
Derivative [Line Items]
Derivative asset, fair value	0	0
Derivative liability, fair value	0	$ 0
Foreign Currency Derivative Instruments
Derivative [Line Items]
Derivative asset, fair value	0
Derivative asset, netting	0
Derivative asset	0
Foreign Currency Derivative Instruments | Quoted Price in Active Markets (Level 1)
Derivative [Line Items]
Derivative asset, fair value	0
Foreign Currency Derivative Instruments | Significant Other Inputs (Level 2)
Derivative [Line Items]
Derivative asset, fair value	0
Foreign Currency Derivative Instruments | Significant Unobservable Inputs (Level 3)
Derivative [Line Items]
Derivative asset, fair value	0
Preferred Units Embedded Derivative
Derivative [Line Items]
Derivative liability, fair value	94
Derivative liability, netting	0
Derivative liability	94
Preferred Units Embedded Derivative | Quoted Price in Active Markets (Level 1)
Derivative [Line Items]
Derivative liability, fair value	0
Preferred Units Embedded Derivative | Significant Other Inputs (Level 2)
Derivative [Line Items]
Derivative liability, fair value	0
Preferred Units Embedded Derivative | Significant Unobservable Inputs (Level 3)
Derivative [Line Items]
Derivative liability, fair value	$ 94