DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES - Schedule of Derivative Assets and Liabilities Measured at Fair Value (Details) - Recurring - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Assets:
Derivative asset	$ 0	$ 11
Liabilities:
Derivative liability	199	192
Commodity derivative instruments
Assets:
Derivative asset, fair value		11
Derivative asset, netting		0
Derivative asset		11
Liabilities:
Derivative liability, fair value	32
Derivative liability, netting	0
Derivative liability	32
Commodity derivative instruments | Quoted Price in Active Markets (Level 1)
Assets:
Derivative asset, fair value		0
Liabilities:
Derivative liability, fair value	0
Commodity derivative instruments | Significant Other Inputs (Level 2)
Assets:
Derivative asset, fair value		11
Liabilities:
Derivative liability, fair value	32
Commodity derivative instruments | Significant Unobservable Inputs (Level 3)
Assets:
Derivative asset, fair value		0
Liabilities:
Derivative liability, fair value	0
Pipeline capacity embedded derivatives
Liabilities:
Derivative liability, fair value	47	53
Derivative liability, netting	0	0
Derivative liability	47	53
Pipeline capacity embedded derivatives | Quoted Price in Active Markets (Level 1)
Liabilities:
Derivative liability, fair value	0	0
Pipeline capacity embedded derivatives | Significant Other Inputs (Level 2)
Liabilities:
Derivative liability, fair value	47	53
Pipeline capacity embedded derivatives | Significant Unobservable Inputs (Level 3)
Liabilities:
Derivative liability, fair value	0	0
Preferred Units embedded derivative
Liabilities:
Derivative liability, fair value	120	139
Derivative liability, netting	0	0
Derivative liability	120	139
Preferred Units embedded derivative | Quoted Price in Active Markets (Level 1)
Liabilities:
Derivative liability, fair value	0	0
Preferred Units embedded derivative | Significant Other Inputs (Level 2)
Liabilities:
Derivative liability, fair value	0	0
Preferred Units embedded derivative | Significant Unobservable Inputs (Level 3)
Liabilities:
Derivative liability, fair value	$ 120	$ 139