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Stock-Based Compensation (Performance Stock Units) (Details) - USD ($)
$ / shares in Units, $ in Millions
1 Months Ended 12 Months Ended
Nov. 30, 2016
May 31, 2016
May 31, 2015
Nov. 30, 2014
Sep. 30, 2014
Aug. 31, 2014
Jul. 31, 2014
May 31, 2014
Apr. 30, 2014
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Unvested activity                        
Nonvested at the beginning of the period (in shares)                   315,212    
Granted (in shares)                   536,773    
Forfeited (in shares)                   (63,217)    
Cancellations (in shares)                   (96,206)    
Nonvested at the end of the period (in shares)                   692,562 315,212  
Performance Stock Units                        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                        
Performance period                   3 years    
Fair value assumptions                        
Risk-free interest rate (as a percent) 0.96% 0.84% 0.83% 0.55% 0.72% 0.67% 0.74%   0.75%      
Dividend yield (as a percent) 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00%   0.00%      
Expected Life (Years) 2 years 51 days 2 years 237 days 2 years 237 days 2 years 1 month 6 days 2 years 3 months 15 days 2 years 5 months 3 days 2 years 5 months 3 days   2 years 8 months 24 days      
Volatility 35.20% 33.30% 28.50% 26.30% 25.70% 26.90% 26.90%   34.30%      
Fair value of award (in dollars per share) $ 17.84 $ 7.19 $ 14.48 $ 7.42 $ 15.26 $ 21.86 $ 22.31   $ 18.00 $ 7.38    
Recognized stock-based compensation expense                   $ 2.5 $ 1.4 $ 0.9
Unrecognized stock-based compensation expense                   $ 3.3    
Unrecognized stock-based compensation expense, period of recognition                   1 year 256 days    
Unvested activity                        
Granted (in shares) 9,524 527,249 237,063 3,906 4,980 26,550 11,487 82,526 15,700      
Weighted Average Grant Date Fair Value                        
Nonvested at the beginning of the period (in dollars per share)                   $ 16.94    
Granted (in dollars per share) $ 17.84 $ 7.19 $ 14.48 $ 7.42 $ 15.26 $ 21.86 $ 22.31   $ 18.00 7.38    
Forfeited (in dollars per share)                   12.78    
Cancellations (in dollars per share)                   21.69    
Nonvested at the end of the period (in dollars per share)                   $ 9.25 $ 16.94  
Performance Stock Units | May 2014 Grant 1                        
Fair value assumptions                        
Risk-free interest rate (as a percent)               0.70%        
Dividend yield (as a percent)               0.00%        
Expected Life (Years)               2 years 7 months 26 days        
Volatility               31.80%        
Fair value of award (in dollars per share)               $ 25.26        
Weighted Average Grant Date Fair Value                        
Granted (in dollars per share)               $ 25.26        
Performance Stock Units | May 2014 Grant 2                        
Fair value assumptions                        
Risk-free interest rate (as a percent)               0.63%        
Dividend yield (as a percent)               0.00%        
Expected Life (Years)               2 years 7 months 11 days        
Volatility               30.10%        
Fair value of award (in dollars per share)               $ 27.53        
Weighted Average Grant Date Fair Value                        
Granted (in dollars per share)               $ 27.53        
Performance Stock Units | Minimum                        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                        
Payout of PSUs (percent of initial grant)                   0.00%    
Performance Stock Units | Maximum                        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                        
Payout of PSUs (percent of initial grant)                   200.00%