STOCK-BASED COMPENSATION - Stock option activity (Details) - USD ($) shares in Thousands, $ in Thousands	6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021
Option Shares
Proceeds from stock option exercises and ESPP purchases	$ 206	$ 336
Options
Option Shares
Outstanding at the beginning of the period (in shares)	747	756
Granted (in shares)	36	84
Exercised (in shares)	(1)	(5)
Forfeited (in shares)	(37)	(58)
Outstanding at the end of the period (in shares)	745	777
Inducement Grants
Option Shares
Outstanding at the beginning of the period (in shares)	241	180
Granted (in shares)		61
Outstanding at the end of the period (in shares)	241	241