STOCK-BASED COMPENSATION - Options activity (Details) - Stock Option and Grant Plan 2019 $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2023 USD ($) $ / shares shares
Options
Outstanding at beginning of period (in shares) | shares	43,380,290
Exercised (in shares) | shares	(199,109)
Cancelled/forfeited (in shares) | shares	(2,917,884)
Outstanding at end of period (in shares) | shares	40,263,297
Vested (in shares) | shares	14,098,417
Vested and expected to vest (in shares) | shares	40,263,297
Weighted-Average Exercise Price
Outstanding at beginning of period (in dollars per share) | $ / shares	$ 3.52
Exercised (in dollars per share) | $ / shares	0.64
Cancelled/forfeited (in dollars per share) | $ / shares	3.63
Outstanding at end of period (in dollars per share) | $ / shares	3.53
Vested (in dollars per share) | $ / shares	3.13
Vested and expected to vest (in dollars per share) | $ / shares	$ 3.53
Contractual Term and Aggregate Intrinsic Value
Weighted average contractual term (in years)	8 years 6 months 25 days
Vested, weighted average contractual term (in years)	8 years 3 months
Vested and expected to vest, weighted average contractual term (in years)	8 years 6 months 25 days
Aggregate intrinsic value | $	$ 3,772
Vested, aggregate intrinsic value | $	2,252
Vested and expected to vest, aggregate intrinsic value | $	$ 3,772