Quarterly report pursuant to Section 13 or 15(d)

Stock Plans - Schedule of Stock Option Activity (Detail)

v3.10.0.1
Stock Plans - Schedule of Stock Option Activity (Detail) - USD ($)
$ / shares in Units, $ in Thousands
9 Months Ended 12 Months Ended
Sep. 30, 2018
Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Weighted-Average Aggregate Intrinsic Value $ 3,240 $ 44,974
Weighted-Average Aggregate Intrinsic Value, Exercisable $ 2,791  
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 895,591  
Options Exercised (146,513)  
Options Forfeited (425,767)  
Options Expired (5,750)  
Options, Outstanding, Ending Balance 5,120,155 4,802,594
Options, Exercisable at September 30, 2018 2,503,062  
Weighted-Average Exercise Price, Outstanding, Beginning Balance $ 13.89  
Weighted-Average Exercise Price, Options Granted 14.22  
Weighted-Average Exercise Price, Options Exercised 3.69  
Weighted-Average Exercise Price, Options Forfeited 16.88  
Weighted-Average Exercise Price, Options Expired 14.32  
Weighted-Average Exercise Price, Outstanding, Ending Balance 13.99 $ 13.89
Weighted-Average Exercise Price, Exercisable $ 13.26  
Weighted-Average Remaining Contractual Term, Outstanding 8 years 8 months 1 day 9 years 2 months 1 day
Weighted-Average Remaining Exercisable 8 years 3 months 29 days