SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Summary of Common Shares Excluded from EPS Calculations (Details) - shares	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Shares excluded from the calculation of EPS	35,081,503	24,503,878
Outstanding warrants
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Shares excluded from the calculation of EPS	27,944,544	19,556,108
Outstanding options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Shares excluded from the calculation of EPS	7,089,524	4,743,537
Unvested restricted stock units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Shares excluded from the calculation of EPS	47,435	204,233