Quarterly report pursuant to Section 13 or 15(d)

Stockholder's Equity - Additional Information (Details)

v3.21.2
Stockholder's Equity - Additional Information (Details) - USD ($)
$ in Thousands
3 Months Ended 9 Months Ended 12 Months Ended
Sep. 30, 2021
Jun. 30, 2021
Mar. 31, 2021
Sep. 30, 2020
Jun. 30, 2020
Mar. 31, 2020
Sep. 30, 2021
Sep. 30, 2020
Dec. 31, 2013
Dec. 31, 2006
Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                      
Total unrecognized compensation cost related to nonvested shares of common stock granted $ 41,400           $ 41,400        
Weighted average period of cost recognized             3 years 10 days        
Compensation expense related to nonvested stock grants             $ 11,700 $ 11,100      
Price of shares issued under Employee Stock Purchase Plan as a percentage of FMV                   95.00%  
Number of shares reserved for the Employee Stock Purchase Plan (in shares)                   250,000  
Additional shares authorized for issuance (in shares)                 250,000    
Treasury shares redeemed to pay income tax $ 840 $ 1,213 $ 9,541 $ 966 $ 1,139 $ 6,933          
Employee                      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                      
Shares redeemed to satisfy personal tax obligations (in shares)             61,177        
Treasury shares redeemed to pay income tax             $ 11,600        
2018 Long-Term Incentive Plan                      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                      
Common stock reserved for issuance (in shares)                     2,210,544
Common stock available for issuance (in shares)                     1,747,099
2018 Long-Term Incentive Plan | Employee                      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                      
Period of vested shares             5 years        
Nonvested stock grants to employees (in shares)             109,665        
2018 Long-Term Incentive Plan | Consultants                      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                      
Nonvested stock grants to employees (in shares)             5,735        
Second Amended and Restated 2005 Non-Employee Directors Compensation Plan                      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                      
Period of vested shares             1 year        
Second Amended and Restated 2005 Non-Employee Directors Compensation Plan | Director                      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                      
Nonvested stock grants to Independent directors (in shares)             7,200        
Percentage of directors' stock grant vested on one year anniversary date             100.00%        
Second Amended and Restated 2005 Non-Employee Directors Compensation Plan | Lead Director                      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                      
Nonvested stock grants to Independent directors (in shares)             3,500        
Percentage of directors' stock grant vested on one year anniversary date             33.33%        
Percentage of directors stock grant vested on grant date             33.33%        
Percentage of directors stock grant vested on two year anniversary date             33.33%