RESTRUCTURING CHARGE - Schedule of changes in accrued restructuring charge (Details) - USD ($)	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Restructuring Reserve [Roll Forward]
Balance, beginning of period	$ 624,000	$ 727,000
Restructuring charge	0	0
Cash paid	(27,000)	(28,000)
Non-cash items	2,000	3,000
Balance, end of period	$ 599,000	$ 702,000