SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Antidilutive Securities Excluded from Computation of Earnings Per Share (Details) - shares shares in Thousands	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	1,471	1,904
Preferred Stock
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	0	290
Stock Options
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	213	683
Warrants
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	41	85
Restricted Stock Units
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	1,217	846