Stockholders' Equity - Summary of Stock Option Activity (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Number of shares, Outstanding at beginning of period	2,712,954
Number of shares, Granted	618,174
Number of shares, Exercised	(63,295)
Number of shares, Forfeitures	(201,989)
Number of shares, Outstanding at end of period	3,065,844
Weighted average exercise price per share, Outstanding at beginning of period	$ 2.98
Weighted average exercise price per share, Granted	2.50
Weighted average exercise price per share, Exercised	2.05
Weighted average exercise price per share, Forfeitures	4.64
Weighted average exercise price per share, Outstanding at end of period	$ 2.80
Aggregate intrinsic value, Outstanding, balance	$ 292	$ 1,190