Net Income (Loss) Per Share - Schedule of Earnings Per Share, Basic and Diluted (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Numerator:
Net income (loss), as reported	$ 695	$ (496)	$ (504)	$ (1,571)
Less: net income (loss) attributable to participating securities	(29)
Net income (loss) available to common shareholders-basic	666	(496)	(504)	(1,571)
Add-back: undistributed earnings allocated to unvested shareholders	0	0	0	0
Less: undistributed earnings reallocated to unvested shareholders	0	0	0	0
Net income (loss) available to common shareholders-diluted	$ 666	$ (496)	$ (504)	$ (1,571)
Basic:
Weighted-average shares of common stock outstanding	42,188,672	41,877,473	42,252,027	41,674,671
Less: weighted-average shares of unvested restricted common stock outstanding	(1,770,364)	(2,220,402)	(1,815,432)	(2,107,417)
Weighted-average number of common shares used in computing basic net income (loss) per common share	40,418,308	39,657,071	40,436,595	39,567,254
Net income (loss) per share applicable to common shareholders-basic	$ 0.02	$ (0.01)	$ (0.01)	$ (0.04)
Net income (loss) available to common shareholders-basic	$ 666	$ (496)	$ (504)	$ (1,571)
Weighted-average shares of common stock outstanding	42,188,672	41,877,473	42,252,027	41,674,671
Less: weighted-average shares of unvested restricted common stock outstanding	(1,770,364)	(2,220,402)	(1,815,432)	(2,107,417)
Weighted-average number of common shares used in computing diluted net income (loss) per common share	40,537,852	39,657,071	40,436,595	39,567,254
Net income (loss) per share applicable to common shareholders-diluted	$ 0.02	$ (0.01)	$ (0.01)	$ (0.04)
Weighted Average [Member]
Basic:
Weighted-average number of common shares issuable upon exercise of outstanding stock options	119,544