Stock-Based Compensation - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock authorized for equity incentive plan (in shares)	20,035,000
Common stock shares issued (in shares	5,120,464
Shares available for issuance (in shares)	3,483,912
Shares of common stock outstanding (in shares)	12,612,196
Stock-based compensation expense	$ 3,849	$ 3,044	$ 2,868
Weighted average fair value of options granted (in dollars per share)	$ 1.46	$ 0.95	$ 1.35
Total fair value of options vested	$ 2,500	$ 2,000	$ 1,700
Total unrecognized estimated compensation cost	$ 5,300
Weighted average contractual life of unvested options	8 years 8 months 12 days
Aggregate intrinsic value of fully vested option shares	$ 200
Restricted stock vested	1,300	$ 1,000	$ 1,300
Estimated compensation cost of unvested restricted stock	$ 3,100
Expired Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock shares issued (in shares	250,579
Shares of common stock outstanding (in shares)	930,993