Annual report pursuant to Section 13 and 15(d)

Stock Plans - Schedule of Stock Option Activity (Detail)

v3.19.1
Stock Plans - Schedule of Stock Option Activity (Detail) - 2014 Plan Stock Options/Stock Issuance Plan and 2017 Stock Incentive Plan [Member] - USD ($)
$ / shares in Units, $ in Thousands
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Options, Outstanding, Beginning Balance 4,802,594  
Options Granted 1,031,091  
Options Exercised (151,121)  
Options Forfeited (516,419)  
Options Expired (11,454)  
Options, Outstanding, Ending Balance 5,154,691 4,802,594
Options, Exercisable at December 31, 2018 2,743,923  
Weighted-Average Exercise Price, Outstanding, Beginning Balance $ 13.89  
Weighted-Average Exercise Price, Options Granted 13.19  
Weighted-Average Exercise Price, Options Exercised 3.63  
Weighted-Average Exercise Price, Options Forfeited 16.56  
Weighted-Average Exercise Price, Options Expired 14.23  
Weighted-Average Exercise Price, Outstanding, Ending Balance 13.78 $ 13.89
Weighted-Average Exercise Price, Exercisable $ 13.47  
Weighted-Average Remaining Contractual Term, Outstanding 8 years 4 months 28 days 9 years 2 months 1 day
Weighted-Average Remaining Exercisable 8 years 14 days  
Weighted-Average Aggregate Intrinsic Value $ 707 $ 44,712
Weighted-Average Aggregate Intrinsic Value, Exercisable $ 677