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Share-Based Compensation Plans - Narrative (Details) - USD ($)
$ 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]      
Shares authorized under employee stock purchase plan (in shares) 3,250,000    
Shares available for grant or issuance under share-based compensation plans (in shares) 1,023,299    
Compensation expense to be recognized $ 8,600    
Maximum vesting period 3 years    
Tax benefit from exercise of stock options $ 1,900 $ 2,600 $ 3,600
Excess tax benefit from share-based compensation 191 984 1,646
Total intrinsic value of options exercised $ 1,200 1,200 2,700
Options that were exercisable (in shares) 0    
Total intrinsic value of options outstanding and exercisable   1,200 1,400
Awards of Stock Units      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Compensation expense $ 11,200 $ 11,400 $ 11,000
Restricted Stock Units (RSUs)      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Shares vested, but issuance deferred (in shares) 63,907    
Issuance deferral period 5 years    
Employee Stock Purchase Plan (in shares)      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Shares authorized under employee stock purchase plan (in shares) 3,000,000