Annual report pursuant to Section 13 and 15(d)

Stock Based Compensation - Equity Incentive Plan - Additional Information (Detail)

v3.10.0.1
Stock Based Compensation - Equity Incentive Plan - Additional Information (Detail) - USD ($)
12 Months Ended
Apr. 30, 2015
Dec. 31, 2018
Dec. 31, 2017
May 16, 2018
Dec. 28, 2017
Mar. 31, 2014
Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Employee contribution through payroll withholdings   $ 531,797 $ 869,066        
Performance Share Units [Member]              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Share-based compensation arrangement by share-based payment award, number of shares authorized 1,310,104     2,710,104      
Common stock, capital shares reserved for future issuance       1,400,000      
Share-based compensation arrangement by share-based payment award, number of shares available for grant   1,431,951          
Restricted Stock Units (RSUs) [Member]              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Share-based compensation arrangement by share-based payment award, equity instruments other than options, grants in period   1,378,301          
Employee Stock Purchase Plan [Member]              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Common stock, capital shares reserved for future issuance 600,000            
Share-based compensation arrangement by share-based payment award, number of shares available for grant   343,753          
Lowest percentage of annual compensation to be utilized by an employee for the plan 1.00%            
Highest percentage of annual compensation to be utilized by an employee for the plan 10.00%            
Maximum number of shares permitted to purchase 7,500            
Offering period 6 months            
Exercise price discount from fair value on offering date 85.00%            
Exercise price discount from fair value on exercise date 85.00% 15.00%          
Share-based compensation arrangement by share-based payment award, terms of award   In April 2015, the Company’s board of directors approved the ESPP, under which 600,000 shares of common stock have been reserved for purchase by the Company’s employees, subject to approval by the stockholders. On May 21, 2015, the Company’s stockholders approved the ESPP. Employees may designate an amount not less than 1% but not more than 10% of their annual compensation, but for not more than 7,500 shares during an offering period. An offering period shall be six months in duration commencing on or about January 1 and July 1 of each year. The exercise price of the option will be the lesser of 85% of the fair market of the common stock on the first business day of the offering period and 85% of the fair market value of the common stock on the applicable exercise date.          
Share-based compensation arrangement by share-based payment award, equity instruments other than options, grants in period   62,168 62,700        
2013 Equity Incentive Plan [Member]              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Share-based compensation arrangement by share-based payment award, number of shares authorized       6,085,967     4,485,967
Common stock, capital shares reserved for future issuance       1,600,000      
Common stock to be issued   1,707,485          
Non-Employee Equity Compensation Plan 2014 [Member]              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Share-based compensation arrangement by share-based payment award, number of shares authorized       850,000   600,000  
Common stock, capital shares reserved for future issuance       250,000      
Common stock available to be issued   366,829          
2017 Equity Inducement Plan [Member]              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Common stock available to be issued   271,000          
2017 Equity Inducement Plan [Member] | Restricted Stock Units (RSUs) [Member]              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Common stock, capital shares reserved for future issuance         600,000