Net Income Per Share - Components of Computation of Basic and Diluted Net Income Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Numerator
Net income	$ 2,132	$ 1,270	$ 651	$ 586	$ 854	$ 838	$ 639	$ 373	$ 4,639	$ 2,704	$ 1,051
Denominator
Weighted average common shares outstanding, basic									16,565	16,236	15,201
Options to purchase common stock									437	535	676
Restricted stock units									27	42	51
Employee stock purchase plan									3	1	3
Weighted average common shares outstanding, diluted									17,032	16,814	15,931
Net income per share
Basic									$ 0.28	$ 0.17	$ 0.07
Diluted	$ 0.12	$ 0.07	$ 0.04	$ 0.03	$ 0.05	$ 0.05	$ 0.04	$ 0.02	$ 0.27	$ 0.16	$ 0.07