XML 20 R49.htm IDEA: XBRL DOCUMENT v3.19.3
Stock-Based Compensation - Summary of Company's Option Activity (Detail) - Employee Stock Option [Member]
$ / shares in Units, $ in Thousands
9 Months Ended 12 Months Ended
Sep. 30, 2019
USD ($)
$ / shares
shares
Dec. 31, 2018
USD ($)
$ / shares
shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]    
Number of Shares Outstanding, Beginning Balance | shares 3,779,403  
Number of Shares, Granted | shares 1,397,699  
Number of Shares, Exercised | shares (23,906)  
Number of Shares, Forfeited | shares (280,099)  
Number of Shares Outstanding, Ending Balance | shares 4,873,097 3,779,403
Number of Shares, Vested and expected to vest | shares 4,873,097  
Number of Shares, Options exercisable | shares 1,714,765  
Weighted Average Exercise Price Outstanding, Beginning Balance | $ / shares $ 7.78  
Weighted Average Exercise Price, Granted | $ / shares 9.06  
Weighted Average Exercise Price, Exercised | $ / shares 5.54  
Weighted Average Exercise Price, Forfeited | $ / shares 9.15  
Weighted Average Exercise Price Outstanding, Ending Balance | $ / shares 8.07 $ 7.78
Weighted Average Exercise Price, Vested and expected to vest | $ / shares 8.07  
Weighted Average Exercise Price, Options exercisable | $ / shares $ 7.08  
Weighted Average Contractual Term (in years) Outstanding 8 years 5 months 8 days 8 years 9 months 18 days
Weighted Average Contractual Term (in years), Vested and expected to vest 8 years 5 months 8 days  
Weighted Average Contractual Term (in years), Options exercisable 7 years 8 months 4 days  
Aggregate Intrinsic Value Outstanding, Beginning Balance | $ $ 1,575 $ 110
Aggregate Intrinsic Value, Vested and expected to vest | $ 1,575  
Aggregate Intrinsic Value, Options exercisable | $ $ 1,043