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Shareholders' Equity - Additional Information (Details) - USD ($)
$ / shares in Units, $ in Millions
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Apr. 07, 2016
Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized 1,394,204        
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant 952,454        
Compensation cost not yet recognized, period for recognition 1 year 3 months 18 days        
Profit Sharing and 401(k) Plan (the “401(k) Plan”), Shares in 401(k) Plan 1,306,366        
Employee Stock Purchase Plan, Maximum Payroll Deduction 15.00%        
Employee Stock Purchase Plan, Percent of Total Share Value 95.00%        
Proceeds from ESPP $ 0.9 $ 0.8 $ 0.8    
Shares from ESPP 17,825 16,413 16,717    
Stock Repurchase Program, Authorized Amount $ 10.0     $ 200.0  
Stock Repurchase Program, Number of Shares Authorized to be Repurchased 252,000        
Stock Repurchase Program, Average Price per Share $ 39.64        
Employee Stock Option [Member]          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Outstanding, ending balance (in shares) 0        
Restricted Stock [Member]          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Outstanding, ending balance (in shares) 0 0 0    
Restricted Stock Units (RSUs) [Member]          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Outstanding, ending balance (in shares) 443 524 681   451
Allocated Share-based Compensation Expense $ 14.8 $ 15.8 $ 13.4    
Allocated Share-based Compensation Expense, Net of Tax 12.4 11.4 9.2    
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Total Grant Date Fair Value 15.4 $ 16.7 $ 11.5    
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized $ 8.9