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Stock-Based Compensation - Restricted Stock Activity (Details) - Restricted Stock [Member] - USD ($)
$ / shares in Units, $ in Millions
12 Months Ended
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Award vesting percentage per year 25.00%    
Period for share issuance after vesting 30 days    
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]      
Outstanding (in shares) 294,680    
Granted (in shares) 237,001 74,772  
Vested (in shares) (138,949)    
Forfeited (in shares) (118,087)    
Outstanding (in shares) 274,645 294,680  
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Roll Forward]      
Outstanding, weighted-average grant date fair value (in dollars per share) $ 49.19    
Granted, weighted-average grant date fair value (in dollars per share) 42.91 $ 75.40 $ 55.14
Vested, weighted-average grant date fair value (in dollars per share) 39.34    
Forfeited, weighted-average grant date fair value (in dollars per share) 47.26    
Outstanding, weighted-average grant date fair value (in dollars per share) $ 49.55 $ 49.19  
Total compensation cost not yet recognized $ 9.2 $ 9.8  
Total compensation cost not yet recognized, period for recognition 2 years 5 months 20 days 2 years 5 months 2 days  
Total fair value of shares vested $ 6.6 $ 9.2 $ 6.5