Calculation of Basic and Diluted Net Income Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Numerator:
Net income	$ 5,850	$ 3,388	$ 13,865	$ 7,899
Denominator (in thousands):
Basic weighted-average common stock outstanding	21,946	21,025	21,687	20,718
Effect of stock-based awards	737	858	793	677
Diluted weighted average common stock outstanding	22,683	21,883	22,480	21,395
Basic net income per share	$ 0.27	$ 0.16	$ 0.64	$ 0.38
Diluted net income per share	$ 0.26	$ 0.15	$ 0.62	$ 0.37