MEZZANINE EQUITY, COMMON STOCK AND STOCKHOLDERS' (DEFICIT) EQUITY - SCHEDULE OF ACTIVITY RELATED TO TIME-BASED AND MARKET-BASED RSUs (Details) - USD ($)	3 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Sep. 30, 2021	Dec. 31, 2020
Time-Based RSUs
Number of RSUs
Unvested restricted stock, beginning balance (in shares)		47,711,649
Granted (in shares)		28,635,488
Vested (in shares)		(23,261,472)
Forfeited (in shares)		(2,442,812)
Unvested restricted stock, ending balance (in shares)	50,642,853	50,642,853	47,711,649
Weighted- average grant date fair value
Unvested restricted stock, Weighted-average grant date fair value, beginning balance (in dollars per share)		$ 10.84
Granted, Weighted-average grant date fair value (in dollars per share)		40.76
Vested, Weighted-average grant date fair value (in dollars per share)		17.94
Forfeited, weighted-average grant date fair value (in dollars per share)		24.37
Unvested restricted stock, Weighted-average grant date fair value, ending balance (in dollars per share)	$ 32.20	$ 32.20	$ 10.84
Share-based Payment Award, Vested	$ 898,800,000	$ 898,800,000	$ 0
Market-Based RSUs
Number of RSUs
Unvested restricted stock, beginning balance (in shares)		27,663,658
Granted (in shares)		35,520,000
Vested (in shares)		(4,149,548)	0
Forfeited (in shares)		0
Unvested restricted stock, ending balance (in shares)	59,034,110	59,034,110	27,663,658
Weighted- average grant date fair value
Unvested restricted stock, Weighted-average grant date fair value, beginning balance (in dollars per share)		$ 0.29
Granted, Weighted-average grant date fair value (in dollars per share)		22.68
Vested, Weighted-average grant date fair value (in dollars per share)		2.34
Forfeited, weighted-average grant date fair value (in dollars per share)		0
Unvested restricted stock, Weighted-average grant date fair value, ending balance (in dollars per share)	$ 23.46	$ 23.46	$ 0.29
Share-based Payment Award, Vested	$ 157,400,000	$ 157,400,000