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Stock-Based Compensation - Additional Information (Detail) - USD ($)
$ / shares in Units, $ in Thousands
1 Months Ended 12 Months Ended
Sep. 15, 2020
Mar. 15, 2020
Sep. 13, 2019
Mar. 15, 2019
Sep. 14, 2018
Mar. 15, 2018
Oct. 08, 2015
Feb. 29, 2020
Mar. 31, 2019
Feb. 28, 2019
Mar. 31, 2018
Mar. 31, 2017
Mar. 31, 2016
Jul. 31, 2015
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Jul. 17, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                    
Vesting period                             4 years      
Total stock-based compensation expense                             $ 63,888 $ 40,664 $ 27,593  
Purchase price of common stock by employees                             85.00%      
Issuance of common stock under employee stock purchase plan                             $ 7,082 5,521 3,637  
Options to Purchase Common Stock                                    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                    
Unrecognized compensation, recognition period                             6 months      
Unrecognized compensation cost, stock options                             $ 500      
Stock options vested, fair value                             2,200 $ 3,700 $ 5,100  
Stock options granted, weighted-average grant date fair value (in dollars per share)                                 $ 11.86  
RSUs and PSUs                                    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                    
Unrecognized compensation cost, restricted stock                             $ 121,900      
Unrecognized compensation, recognition period                             2 years 3 months 18 days      
2015 Plan                                    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                    
Number of shares of common stock reserved for future issuance (in shares)                           800,000        
Share-based compensation, increase in number of shares reserved and available for issuance as percentage under the plan                           4.00%        
Increase in number of shares authorized (in shares)             1,500,000 1,996,444 1,904,017   1,762,149 1,702,187 1,661,616          
Number of shares authorized (in shares)                             15,788,542      
Shares available for grant (in shares)                             2,305,220      
2020 Bonus Plan                                    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                    
Total stock-based compensation expense                             $ 2,500      
Employee Stock Purchase Plan                                    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                    
Number of shares of common stock reserved for future issuance (in shares)                                   800,000
Increase in number of shares authorized (in shares)               499,111   476,004 440,537 425,547 415,404          
Number of shares authorized (in shares)                             3,056,603      
Shares available for grant (in shares)                             1,824,947      
Issuance of common stock under ESPP (in shares) 131,585 101,806 74,221 110,822 96,108 123,607                        
Share issued, price per share (in dollars per share) $ 28.39 $ 32.87                                
Issuance of common stock under employee stock purchase plan $ 3,700 $ 3,300 $ 2,900 $ 2,600 $ 2,000 $ 1,600                        
Employee Stock Purchase Plan | Minimum                                    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                    
Stock options granted, weighted-average grant date fair value (in dollars per share)                             $ 9.63 $ 14.17 6.62  
Share issued, price per share (in dollars per share)     $ 30.46 $ 30.46 $ 21.96 $ 12.96                        
Employee Stock Purchase Plan | Maximum                                    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                    
Stock options granted, weighted-average grant date fair value (in dollars per share)                             $ 22.30 $ 17.94 $ 10.95  
Employee withholding percentage                             15.00%      
Share issued, price per share (in dollars per share)     $ 42.22 $ 21.96 $ 14.78 $ 14.78