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Share-Based Compensation (Narrative) (Details) - USD ($)
3 Months Ended
Mar. 31, 2018
Mar. 31, 2017
Share-Based Compensation [Line Items]    
Number of shares available for grant 982,458  
Expected life 5 years 2 months 12 days  
Expected volatility 42.01%  
Risk-free rate 2.36%  
Quarterly dividends $ 0  
Share-based compensation expense 6,081,000 $ 4,306,000
Unamortized share-based compensation expense $ 38,900,000  
Weighted average period over which unrecognized compensation cost is expected to be recognized 2 years 3 months 18 days  
Restricted Stock Units [Member]    
Share-Based Compensation [Line Items]    
Units granted 514,000 665,000
Weighted-average per share prices $ 26.49 $ 30.48
Stock Options [Member]    
Share-Based Compensation [Line Items]    
Stock options awarded 479,000 265,000
Weighted-average exercise prices $ 24.53 $ 23.47
Weighted average grant date fair value $ 11.82 $ 13.70
Unrestricted Stock Units [Member]    
Share-Based Compensation [Line Items]    
Units granted 10,000  
Weighted-average per share prices $ 25.40