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Stock-Based Compensation - Schedule of Restricted Stock Activity (Details) - USD ($)
$ / shares in Units, $ in Millions
12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Stock compensation expense $ 8.0 $ 5.6 $ 3.8
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Roll Forward]      
Ending Balance $ 2,013.9 1,693.9  
Restricted Stock      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Stock issued during period, shares, restricted stock award 230,922    
Stock compensation expense   $ 5.6 3.3
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]      
Restricted stock, beginning of year, number of shares 380,584    
Granted, number of shares 230,922    
Vested, number of shares (202,286)    
Forfeited, number of shares (46,198)    
Canceled, number of shares 0    
Restricted stock, end of year, number of shares 363,022 380,584  
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Roll Forward]      
Restricted stock, beginning of year, weighted-average measurement date fair value (in dollars per share) $ 37.46    
Granted, weighted average grant date fair value (in dollars per share)   $ 41.29  
Vested, weighted average grant date fair value (in dollars per share)   33.24  
Forfeited, weighted average grant date fair value (in dollars per share)   41.18  
Canceled, weighted average grant date fair value (in dollars per share)   0  
Restricted stock, end of year, weighted-average measurement date fair value (in dollars per share) $ 41.47 $ 37.46  
Tax benefits from stock-based compensation $ 0.4 $ 0.2 0.6
Unrecognized compensation cost related to nonvested restricted stock awards $ 8.1    
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition 1 year 1 month 6 days    
Common Stock      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Stock compensation expense $ 8.0 $ 5.6 $ 3.8
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Roll Forward]      
Ending Balance $ 1,049.3    
Upon Achievement of Defined Total Return to Shareholder Goals | Restricted Stock      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Stock issued during period, shares, restricted stock award 36,463