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Stock-based Compensation - Narrative (Details) - USD ($)
 1 Months Ended 3 Months Ended 12 Months Ended
Sep. 30, 2019
Mar. 31, 2021
Mar. 31, 2020
Dec. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Stock options granted (in shares)   0    
Total grant date fair value for vested options   $ 5,800,000 $ 1,900,000  
Issuance of common stock in connection with acquisition (in shares)   948,000    
Stock-based compensation expense   $ 18,038,000 $ 12,897,000  
Class A common stock | 2019 Equity Incentive Plan        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Number of shares authorized for issuance (in shares)   66,661,953    
Number of new shares authorized for issuance (in shares)   29,335,000    
Number of additional shares authorized for issuance (in shares)   37,326,953    
Class A and Class B Common Stock | 2019 Equity Incentive Plan        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Potential increase in number of shares authorized, as a percentage of total common stock outstanding   5.00%    
Options        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Weighted-average grant date fair value for options granted (in dollars per share)     $ 7.28  
Unvested options exercisable (in shares)   9,524,663   10,765,894
Options unrecognized stock-based compensation expense   $ 18,200,000   $ 20,600,000
Weighted-average remaining vesting period   2 years 4 months 24 days   2 years 7 months 6 days
Liability for early exercise of stock options   $ 7,500,000   $ 8,600,000
Number of unvested shares expected to be repurchased (in shares)   3,389,697   3,871,772
Options | 2010 Equity Incentive Plan        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Vesting period   4 years    
Expiration period   10 years    
Options | Common stock | 2010 Equity Incentive Plan        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Exercise price of common stock, percentage of fair market value   100.00%    
Restricted Stock Units (RSUs)        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Vesting period   4 years    
Weighted-average remaining vesting period   3 years 6 months   3 years 6 months
Number of shares vested during the period (in shares)   649,000    
Stock-based compensation expense   $ 13,600,000 $ 8,800,000  
Unrecognized stock-based compensation expense   176,200,000   $ 141,800,000
Total grant date fair value for vested shares   $ 9,900,000 4,800,000  
Restricted Stock        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Issuance of unvested restricted stock in connection with acquisition (in shares)   841,000    
Number of shares vested during the period (in shares)   0    
Restricted stock issued in connection with acquisition, aggregate grant date fair value     1,800,000  
Stock-based compensation expense   $ 1,400,000 1,400,000  
Unrecognized stock-based compensation expense   $ 7,400,000 $ 13,000,000.0  
Restricted Stock | Tranche One        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Vesting period   2 years    
Vesting percentage   77.80%    
Restricted Stock | Tranche Two        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Vesting period   3 years    
Shares available for issuance under the ESPP | 2019 Employee Stock Purchase Plan        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Weighted-average remaining vesting period   1 month 6 days   4 months 24 days
Unrecognized stock-based compensation expense   $ 700,000   $ 2,000,000.0
Maximum ownership percentage threshold for participation 5.00%      
Maximum contribution percentage per employee 10.00%      
Shares available for issuance under the ESPP | Class A common stock | 2019 Employee Stock Purchase Plan        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Number of additional shares allowable under the plan (in shares) 5,870,000      
Purchase price of common stock, percentage of fair value 85.00%      
Offering period 6 months      
Purchase period 6 months      
Maximum number of shares available for repurchase for each employee (in shares) 1,500      
Maximum value of shares available for repurchase for each employee $ 25,000      
Number of shares repurchased (in shares)   0 0  
Shares available for issuance under the ESPP | Class A and Class B Common Stock | 2019 Employee Stock Purchase Plan        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Potential increase in number of share authorized, as a percentage of total common stock outstanding 1.00%