SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Narrative (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Jul. 23, 2021	Dec. 31, 2020
Accounting Policies [Abstract]
Restricted cash	$ 49,000,000		$ 49,000,000			$ 32,000,000
Write-down of inventory	31,000,000		31,000,000	$ 0
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketing and promotion costs	7,000,000	$ 1,000,000	11,000,000	$ 3,000,000
2021 Convertible Notes | Convertible Debt
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value (carrying amount)	2,958,000,000		2,958,000,000		$ 2,500,000,000
Money Market Funds | Fair Value, Inputs, Level 1 | Fair Value, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds	$ 4,983,000,000		$ 4,983,000,000			$ 2,782,000,000