DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES - Fair Value Measurement Inputs (Details) $ in Millions	3 Months Ended
	Mar. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)
Derivative [Line Items]
Expected timing until exercise of exchange option	5 years 2 months 12 days
Recurring
Derivative [Line Items]
Derivative liability	$ 209	$ 192
Preferred Units embedded derivative | Recurring
Derivative [Line Items]
Derivative liability		$ 139
Significant Unobservable Inputs (Level 3) | Preferred Units embedded derivative | Recurring
Derivative [Line Items]
Derivative liability	$ 156
Significant Unobservable Inputs (Level 3) | Measurement Input, Risk Free Interest Rate | Minimum
Derivative [Line Items]
Embedded derivative liability, measurement input	0.0715
Significant Unobservable Inputs (Level 3) | Measurement Input, Risk Free Interest Rate | Maximum
Derivative [Line Items]
Embedded derivative liability, measurement input	0.1251
Significant Unobservable Inputs (Level 3) | Measurement Input, Interest Rate Volatility
Derivative [Line Items]
Embedded derivative liability, measurement input	0.3875