General form of registration statement for all companies including face-amount certificate companies

Stock-Based Compensation - Stock-based compensation expense (Details)

v3.21.2
Stock-Based Compensation - Stock-based compensation expense (Details) - USD ($)
$ in Thousands
 3 Months Ended 9 Months Ended 12 Months Ended
Sep. 30, 2021
Sep. 30, 2020
Sep. 30, 2021
Sep. 30, 2020
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Share-based payment arrangements information              
Total stock-based compensation expense $ 4,848 $ 1,619 $ 12,100 $ 3,561 $ 20,527 $ 1,680 $ 1,442
Unrecognized stock-based compensation expense 68,900   $ 68,900        
Weighted-average period over which unrecognized stock-based compensation expense are expected to be recognized     1 year 7 months 6 days        
Restricted Stock Units (RSUs)              
Share-based payment arrangements information              
Total stock-based compensation expense           100 100
Unrecognized stock-based compensation expense         $ 15,500    
Weighted-average period over which unrecognized stock-based compensation expense are expected to be recognized         1 year 3 months 18 days    
Share based compensation arrangement by share based payment award, equity instruments other options, vested in period, total grant date fair value     $ 2,900        
Cost of Revenue              
Share-based payment arrangements information              
Total stock-based compensation expense         $ 673 305 219
Product development              
Share-based payment arrangements information              
Total stock-based compensation expense 1,239 212 1,953 465 6,151 450 287
Sales, marketing and customer support              
Share-based payment arrangements information              
Total stock-based compensation expense 1,423 305 3,743 869 13,703 917 930
General and administrative              
Share-based payment arrangements information              
Total stock-based compensation expense $ 2,186 $ 1,102 $ 6,404 $ 2,227 20,527 $ 1,680 $ 1,442
General and administrative | Restricted Stock Units (RSUs)              
Share-based payment arrangements information              
Total stock-based compensation expense         $ 700