STOCK-BASED COMPENSATION - Stock-based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation	$ 699	$ 334	$ 1,795	$ 571
Restricted common stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation	59	0	241	0
Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation	$ 640	$ 334	$ 1,554	$ 571