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Stock-Based Compensation - Additional Information (Details) - USD ($)
$ / shares in Units, $ in Millions
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Number of shares authorized (in shares) 4,900,000    
Shares remaining available for issuance (in shares) 1,900,000    
Share-based compensation expense $ 13.0 $ 15.0 $ 14.0
Intrinsic value of options 1.0 0.0 0.0
Excess tax benefit of options exercised $ 0.4 $ 0.0 $ 0.0
Stock Options      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Expiration period 10 years    
Weighted-average fair value of options granted (in dollars per share) $ 9.07 $ 7.70 $ 15.15
Costs not yet recognized $ 4.0    
Costs not yet recognized, period for recognition 1 year    
Volatility   26.00%  
Restricted Stock Units      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Costs not yet recognized $ 4.0    
Costs not yet recognized, period for recognition 1 year    
Shares granted (in dollars per share) $ 38.16    
Total shareholder return restricted share units      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Costs not yet recognized $ 6.0    
Costs not yet recognized, period for recognition 2 years    
Vesting period 3 years    
Volatility 25.00% 25.00%  
Shares granted (in dollars per share) $ 42.24 $ 38.64  
First 12-month period | Stock Options      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Vesting percentage 30.00%    
Second 12-month period | Stock Options      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Vesting percentage 30.00%    
Third 12-month period | Stock Options      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Vesting percentage 40.00%    
Continuing Operations      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Share-based compensation expense $ 12.0 $ 14.0 $ 13.0
Continuing Operations | Stock Options      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Share-based compensation expense 3.0 5.0 6.0
Continuing Operations | Restricted Stock Units      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Share-based compensation expense 4.0 5.0 $ 8.0
Continuing Operations | Total shareholder return restricted share units      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Share-based compensation expense $ 5.0 $ 4.0