Share-based Compensation - Stock Options and Restricted Stock (Details) - USD ($)
$ in Thousands
3 Months Ended 9 Months Ended
Sep. 30, 2021
Sep. 30, 2020
Sep. 30, 2021
Sep. 30, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Share-based compensation expense $ 3,064 $ 1,347 $ 7,377 $ 4,534
Sales, general and administrative        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Share-based compensation expense 2,396 945 5,473 3,392
Research and development        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Share-based compensation expense $ 668 $ 402 $ 1,904 $ 1,142