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Stock-Based Compensation Narrative (Details)
$ in Millions
9 Months Ended
Sep. 30, 2017
USD ($)
shares
Dec. 31, 2016
USD ($)
Employee Stock Option [Member]    
[Line Items]    
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized $ 3.6  
Unrecognized compensation expense, Expected weighted average period for recognition (years) 1 year 7 months 6 days  
Restricted Stock Units (RSUs) [Member]    
[Line Items]    
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized $ 25.6  
Unrecognized compensation expense, Expected weighted average period for recognition (years) 1 year 9 months 18 days  
Phantom Share Units (PSUs) [Member]    
[Line Items]    
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized $ 3.9  
Unrecognized compensation expense, Expected weighted average period for recognition (years) 1 year 9 months 18 days  
Deferred Compensation Share-based Arrangements, Liability, Current $ 1.4 $ 1.0
Employee Stock Purchase Plan [Member]    
[Line Items]    
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant | shares 348,000  
Stock Incentive Plan [Member]    
[Line Items]    
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized | shares 10,473,956  
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant | shares 4,641,890  
Reduction in stock options available for issue 1  
Authorized share reserve reduction in awards other than stock options or share appreciation rights available for issue, conversion ratio 1.7