Calculation of Basic and Diluted Net Income (Loss) Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Numerator:
Net income (loss)	$ (2,090)	$ 3,908	$ (4,272)	$ 8,015
Denominator (in thousands):
Basic weighted-average common stock outstanding	22,129	21,712	22,139	21,556
Effect of stock -based awards		851		820
Diluted weighted average common stock outstanding	22,129	22,563	22,139	22,376
Basic net income (loss) per share	$ (0.09)	$ 0.18	$ (0.19)	$ 0.37
Diluted net income (loss) per share	$ (0.09)	$ 0.17	$ (0.19)	$ 0.36