Annual report pursuant to Section 13 and 15(d)

Stock Plan and Stock-Based Compensation - Summary of Stock Option Grants, Including Performance Options (Detail)

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Stock Plan and Stock-Based Compensation - Summary of Stock Option Grants, Including Performance Options (Detail)
$ / shares in Units, $ in Thousands
12 Months Ended
Dec. 31, 2018
USD ($)
$ / shares
shares
Shares Subject to Outstanding Options  
Outstanding at the beginning of period | shares 4,356,441
Options granted | shares 2,167,272
Options exercised | shares (750,852)
Options forfeited | shares (179,729)
Outstanding as end of period | shares 5,593,132
Vested and expected to vest | shares 5,593,132
Exercisable | shares 2,627,819
Weighted-Average Exercise Price of Options  
Outstanding at the beginning of period | $ / shares $ 5.15
Options granted | $ / shares 11.84
Options exercised | $ / shares 4.76
Options forfeited | $ / shares 8.81
Outstanding as end of period | $ / shares 7.68
Vested and expected to vest | $ / shares 7.68
Exercisable | $ / shares $ 5.65
Weighted-Average Remaining Contractual Term (Years)  
Outstanding 8 years 14 days
Vested and expected to vest 8 years 14 days
Exercisable 7 years 25 days
Aggregate Intrinsic Value (In Thousands)  
Outstanding | $ $ 11,096
Vested and expected to vest | $ 11,096
Exercisable | $ $ 7,799