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Share-Based Compensation - Options additional information (Details) - USD ($)
$ / shares in Units, $ in Thousands
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Vesting period 3 years    
Options and SARs      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Vesting period 3 years    
Proceeds from stock options exercised $ 5,000    
Tax benefit from exercise of stock options and SARs $ 3,000    
Weighted average grant date fair value $ 8.14 $ 7.90 $ 7.50
Aggregate intrinsic value of options exercised $ 59,723 $ 51,350 $ 43,468