Quarterly report pursuant to Section 13 or 15(d)

Stock Plans - Schedule of Stock Option Activity (Detail)

v3.19.1
Stock Plans - Schedule of Stock Option Activity (Detail) - Stock Options [Member]
$ / shares in Units, $ in Thousands
 3 Months Ended
Mar. 31, 2019
USD ($)
$ / shares
shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Options, Outstanding, Beginning Balance | shares 5,154,691
Options Granted | shares 432,400
Options Exercised | shares (20,050)
Options Forfeited | shares (72,195)
Options Expired | shares (28,948)
Options, Outstanding, Ending Balance | shares 5,465,898
Options Exercisable at March 31, 2019 | shares 3,016,052
Weighted-Average Exercise Price, Outstanding, Beginning Balance | $ / shares $ 13.78
Weighted-Average Exercise Price, Options Granted | $ / shares 5.66
Weighted-Average Exercise Price, Options Exercised | $ / shares 1.50
Weighted-Average Exercise Price, Options Forfeited | $ / shares 12.30
Weighted-Average Exercise Price, Options Expired | $ / shares 12.70
Weighted-Average Exercise Price, Outstanding, Ending Balance | $ / shares 13.21
Weighted-Average Exercise Price, Exercisable | $ / shares $ 13.71
Weighted-Average Remaining Contractual Term, Outstanding 8 years 3 months 10 days
Weighted-Average Remaining Exercisable 7 years 9 months 29 days
Weighted-Average Aggregate Intrinsic Value | $ $ 1,058
Weighted-Average Aggregate Intrinsic Value, Exercisable | $ $ 1,026