DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES - Schedule of Derivative Assets and Liabilities Measured at Fair Value (Details) - Recurring - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
Assets:
Derivative asset	$ 2	$ 11
Liabilities:
Derivative liability	239	192
Commodity derivative instruments
Assets:
Derivative asset, fair value	2	11
Derivative asset, netting	0	0
Derivative asset	2	11
Liabilities:
Derivative liability, fair value	64
Derivative liability, netting	0
Derivative liability	64
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	2	11
Liabilities:
Derivative liability, fair value	64
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	50	53
Derivative liability, netting	0	0
Derivative liability	50	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	50	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	125	139
Derivative liability, netting	0	0
Derivative liability	125	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	125	$ 139
Derivative liability	$ 125