Quarterly report pursuant to Section 13 or 15(d)

Stock Plans - Schedule of Stock Option Activity (Detail)

v3.8.0.1
Stock Plans - Schedule of Stock Option Activity (Detail) - USD ($)
 3 Months Ended 12 Months Ended
Mar. 31, 2018
Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Weighted-Average Aggregate Intrinsic Value $ 6,006 $ 44,974
Weighted-Average Aggregate Intrinsic Value, Exercisable $ 3,992  
2014 Plan Stock Options/Stock Issuance Plan and 2017 Stock Incentive Plan [Member]    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Options, Outstanding, Beginning Balance 4,802,594  
Options Granted 433,341  
Options Exercised (55,541)  
Options Forfeited (245,238)  
Options Expired (1,425)  
Options, Outstanding, Ending Balance 4,933,731 4,802,594
Options,Exercisable at December 31, 2017 1,978,465  
Weighted-Average Exercise Price, Outstanding, Beginning Balance $ 13.89  
Weighted-Average Exercise Price, Options Granted 15.02  
Weighted-Average Exercise Price, Options Exercised 1.80  
Weighted-Average Exercise Price, Options Forfeited 17.46  
Weighted-Average Exercise Price, Options Expired 12.24  
Weighted-Average Exercise Price, Outstanding, Ending Balance 13.95 $ 13.89
Weighted-Average Exercise Price, Exercisable $ 12.80  
Weighted-Average Remaining Contractual Term, Outstanding 9 years 11 days 9 years 2 months 1 day
Weighted-Average Remaining Exercisable 8 years 8 months 16 days