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Retirement Plans (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Retirement Plans      
Minimum percentage of annual eligible compensation by the participants 1.00%    
Maximum percentage of annual eligible compensation by the participants 90.00%    
Percentage of contribution matched 6.00%    
Percentage of contribution, matched 100% by employer 3.00%    
Employer match of employee contributions of first 3% of contributions 100.00%    
Percentage of contribution, matched 50% by employer 3.00%    
Employer match of employee contributions of next 3% of contributions 50.00%    
Vesting percentage 20.00%    
Vesting period 5 years    
Contribution expenses $ 0.7 $ 0.8 $ 0.5