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Stock-based Compensation (Details) - USD ($)
shares in Thousands, $ in Millions
3 Months Ended 9 Months Ended
Sep. 30, 2021
Jun. 30, 2021
Mar. 31, 2021
Sep. 30, 2020
Sep. 30, 2021
Sep. 30, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Options granted (in shares) 10 24 200      
Vesting period     4 years      
RSU            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Restricted stock units granted (in shares) 17 41 400      
RSU | Employee            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Vesting period     4 years      
RSU | Director            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Vesting period     9 months      
Options and RSUs            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Vesting period 4 years 4 years        
Estimated grant date fair value of options and RSUs granted $ 0.3 $ 0.7 $ 5.6      
Stock option compensation expense $ 1.0     $ 1.7 $ 4.7 $ 4.1