NET LOSS PER SHARE - Antidilutive Securities Excluded from Earnings per Share (Details) - shares	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation amount (in shares)	177,417,887	1,029,381,821,000	573,435,179,000
Convertible preferred stock (on an as-converted basis)
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation amount (in shares)	0	957,159,704,000	502,582,535,000
Convertible preferred stock warrants (on an as-converted basis)
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation amount (in shares)	0	1,546,799,000	1,546,799,000
Private warrants to purchase common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation amount (in shares)	44,350,000	0	0
Options outstanding to purchase common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation amount (in shares)	64,119,902	70,675,318,000	69,305,845,000
RSUs outstanding
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation amount (in shares)	32,210,200	0	0
If-converted common shares from convertible note
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation amount (in shares)	36,737,785	0	0