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
	Mar. 31, 2021	Mar. 31, 2020
Numerator:
Net income (loss)	$ 2,036	$ (4,828)
Denominator:
Weighted-average common stock outstanding, basic (in shares)	28,579	31,006
Dilutive effect of potential common shares, Stock options, restricted stock units, restricted stock awards and employee stock purchase plan (in shares)	601	0
Dilutive effect of potential common shares, Total shares, diluted (in shares)	29,180	31,006
Basic net loss per share (in dollars per share)	$ 0.07	$ (0.16)
Diluted net loss per share (in dollars per share)	$ 0.07	$ (0.16)