FAIR VALUE - Put and Call Options Measured at Fair Value (Details) $ in Millions	Mar. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)
Put option | Other long-term liabilities
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair value of financial liability	$ 63	$ 45
Call option | Other long-term assets
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair value of financial asset	$ 440	$ 503
Options | Level 3 fair value measurement | Annualized volatility
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Significant unobservable inputs	0.332	0.299
Options | Level 3 fair value measurement | Secured credit rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Significant unobservable inputs	0.006	0.004
Options | Level 3 fair value measurement | NOPAT
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Significant unobservable inputs	0.120	0.120
Options | Level 3 fair value measurement | Weighted average cost of capital
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Significant unobservable inputs	0.095	0.095
Options | Level 3 fair value measurement | Long term growth rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Significant unobservable inputs	0.030	0.030