DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES - Schedule of Derivative Assets and Liabilities Measured at Fair Value (Details) - Recurring - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Assets:
Derivative asset	$ 38	$ 11
Liabilities:
Derivative liability	209	192
Commodity derivative instruments
Assets:
Derivative asset, fair value	39	11
Derivative asset, netting	(1)	0
Derivative asset	38	11
Liabilities:
Derivative liability, fair value	2
Derivative liability, netting	(1)
Derivative liability	1
Commodity derivative instruments | Quoted Price in Active Markets (Level 1)
Assets:
Derivative asset, fair value	0	0
Liabilities:
Derivative liability, fair value	0
Commodity derivative instruments | Significant Other Inputs (Level 2)
Assets:
Derivative asset, fair value	39	11
Liabilities:
Derivative liability, fair value	2
Commodity derivative instruments | Significant Unobservable Inputs (Level 3)
Assets:
Derivative asset, fair value	0	0
Liabilities:
Derivative liability, fair value	0
Pipeline capacity embedded derivatives
Liabilities:
Derivative liability, fair value	52	53
Derivative liability, netting	0	0
Derivative liability	52	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	52	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	156	139
Derivative liability, netting	0	0
Derivative liability		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	156	$ 139
Derivative liability	$ 156