NET INCOME (LOSS) PER SHARE - RECONCILIATION OF NUMERATORS AND DENOMINATORS USED IN COMPUTING BASIC AND DILUTED NET INCOME (LOSS) PER SHARE (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Numerator:
Net income (loss)	$ 3,771	$ 2,855	$ 11,148	$ (2,685)
Denominator:
Weighted-average common stock outstanding, basic (in shares)	32,474	26,898	30,693	28,507
Dilutive effect of potential common shares, Stock options, restricted stock units, restricted stock awards and employee stock purchase plan (in shares)	138	236	372	0
Dilutive effect of potential common shares, Total shares, diluted (in shares)	32,612	27,134	31,065	28,507
Basic net loss per share (in dollars per share)	$ 0.12	$ 0.11	$ 0.36	$ (0.09)
Diluted net loss per share (in dollars per share)	$ 0.12	$ 0.11	$ 0.36	$ (0.09)