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Stock-based Compensation - Additional Information (Detail) - USD ($)
$ / shares in Units, $ in Millions
1 Months Ended 9 Months Ended
Jan. 31, 2021
Sep. 30, 2021
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]    
Unrecognized stock-based compensation expense   $ 75.7
Unrecognized stock-based compensation, weighted-average period   2 years 6 months
Proceeds from stock options exercised including unsettled options   $ 3.3
2015 Equity Incentive Plan [Member]    
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]    
Additional shares to be issued 1,499,037  
Common stock shares authorized for issuance   13,911,954
Shares available for future grants   2,392,917
Weighted-average fair values of options granted   $ 26.28
Exercise of stock options, Shares   325,273
Total intrinsic value of options exercised   $ 10.1
2015 Employee Stock Purchase Plan [Member]    
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]    
Additional shares to be issued 374,759  
Common stock shares authorized for issuance   998,683
Shares available for future grants   769,174
Common stock shares issued to participants   53,596