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Employee Benefit Plans - Narrative (Details) - USD ($)
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2007
Retirement Benefits [Abstract]        
Eligibility period for 401K savings plan, period 3 months      
401(k) plan, maximum participant deferral percent 60.00%      
401(k) plan, employer match per dollar of participant contribution $ 0.50      
401(k) plan, maximum employer match percentage 10.00%      
401(k) plan, contributions made $ 1,600,000 $ 1,600,000 $ 1,500,000  
Deferred Compensation, maximum participant deferral percent       70.00%
Deferred Compensation, maximum director fees and bonuses that may be deferred (percent)       100.00%
Deferred Compensation, mandatory Company contributions as percentage of gross monthly salary (percent)       10.00%
Deferred Compensation, liability under Plan $ 27,400,000 $ 27,000,000.0