NET INCOME (LOSS) PER SHARE - Calculation of net income per share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
NET INCOME (LOSS) PER SHARE
Net income (loss)	$ (8,340)	$ 1,233
Shares outstanding:
Weighted-average shares - basic (in shares)	21,523	21,544
Additional dilutive common stock equivalents (in shares)	0	61
Diluted shares outstanding (in shares)	21,523	21,605
Net income (loss) per share - basic (in dollars per share)	$ (0.39)	$ 0.06
Net income (loss) per share - diluted (in dollars per share)	$ (0.39)	$ 0.06