STOCK-BASED COMPENSATION - Stock Option Activity (Details) - Stock options - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Number of Shares Outstanding
Beginning balance (in shares)	303,275
Stock options exercised (in shares)	(25,287)
Stock options cancelled (in shares)	(14,745)
Ending balance (in shares)	263,243	303,275
Exercisable (in shares)	263,243
Vested and expected to vest (in shares)	263,243
Weighted-Average Exercise Price
Beginning balance (in dollars per share)	$ 7.63
Stock options exercised (in dollars per share)	7.82
Stock options cancelled (in dollars per share)	7.89
Ending balance (in dollars per share)	7.60	$ 7.63
Exercisable (in dollars per share)	7.60
Vested and expected to vest (in dollars per share)	$ 7.60
Stock option activity
SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2	3 years 4 months 24 days	4 years 4 months 24 days
SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2	3 years 4 months 24 days	4 years 4 months 24 days
Exercisable, Weighted-Average Remaining Contractual Life	3 years 4 months 24 days
Vested and expected to vest, Weighted-Average Remaining Contractual Life	3 years 4 months 24 days
Beginning balance, Aggregate Intrinsic Value	$ 3,393
Ending balance, Aggregate Intrinsic Value	2,782	$ 3,393
Exercisable, Aggregate Intrinsic Value	2,782
Vested and expected to vest, Aggregate Intrinsic Value	$ 2,782