DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES - Derivative Assets and Liabilities Measured at Fair Value (Details) - Recurring - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Commodity Derivative Instruments
Derivative [Line Items]
Derivative asset, fair value	$ 11
Derivative asset, netting	0
Derivative asset	11	$ 9
Derivative liability	192	103
Commodity Derivative Instruments | Quoted Price in Active Markets (Level 1)
Derivative [Line Items]
Derivative asset, fair value	0
Commodity Derivative Instruments | Significant Other Inputs (Level 2)
Derivative [Line Items]
Derivative asset, fair value	11
Commodity Derivative Instruments | Significant Unobservable Inputs (Level 3)
Derivative [Line Items]
Derivative asset, fair value	0
Pipeline capacity embedded derivatives
Derivative [Line Items]
Derivative asset, fair value		8
Derivative asset, netting		0
Derivative asset		8
Derivative liability, fair value	53
Derivative liability, netting	0
Derivative liability	53
Pipeline capacity embedded derivatives | Quoted Price in Active Markets (Level 1)
Derivative [Line Items]
Derivative asset, fair value		0
Derivative liability, fair value	0
Pipeline capacity embedded derivatives | Significant Other Inputs (Level 2)
Derivative [Line Items]
Derivative asset, fair value		8
Derivative liability, fair value	53
Pipeline capacity embedded derivatives | Significant Unobservable Inputs (Level 3)
Derivative [Line Items]
Derivative asset, fair value		0
Derivative liability, fair value	0
Preferred Units embedded derivative
Derivative [Line Items]
Derivative liability, fair value	139	103
Derivative liability, netting	0	0
Derivative liability	139	103
Preferred Units embedded derivative | Quoted Price in Active Markets (Level 1)
Derivative [Line Items]
Derivative liability, fair value	0	0
Preferred Units embedded derivative | Significant Other Inputs (Level 2)
Derivative [Line Items]
Derivative liability, fair value	0	0
Preferred Units embedded derivative | Significant Unobservable Inputs (Level 3)
Derivative [Line Items]
Derivative liability, fair value	$ 139	103
Foreign currency derivative instruments
Derivative [Line Items]
Derivative asset, fair value		1
Derivative asset, netting		0
Derivative asset		1
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		1
Foreign currency derivative instruments | Significant Unobservable Inputs (Level 3)
Derivative [Line Items]
Derivative asset, fair value		$ 0