COMMON STOCK WARRANT LIABILITY - Narrative (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
	Sep. 29, 2021	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Jul. 23, 2021	Dec. 31, 2020	Sep. 30, 2017
Class of Warrant or Right [Line Items]
Number of warrants (in shares)						85,750,000		2
Convertible preferred stock warrant liability		$ 0		$ 0			$ 2,960
Change in fair value of convertible preferred stock warrant liability			$ 100		$ 200
Sponsor earnback warrants vested (in shares)	4,927,778
Private Warrants
Class of Warrant or Right [Line Items]
Number of warrants (in shares)						44,350,000
Convertible preferred stock warrant liability						$ 812,000
Change in fair value of convertible preferred stock warrant liability		$ 24,800		$ 24,800