STOCK-BASED COMPENSATION - Stock option activity (Details) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Option Shares
Proceeds from stock option exercised	$ 0	$ 281
Options [Member]
Option Shares
Outstanding at the beginning of the period (in shares)	756	757
Granted (in shares)	42	8
Exercised (in shares)		(7)
Forfeited (in shares)	(10)	(3)
Outstanding at the end of the period (in shares)	788	755
Inducement Grants [Member]
Option Shares
Outstanding at the beginning of the period (in shares)	180
Granted (in shares)	61
Outstanding at the end of the period (in shares)	241