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Share-Based Compensation (Summary of Assumptions) (Details) - USD ($)
3 Months Ended
Mar. 31, 2017
Mar. 31, 2016
Director and Officers [Member]    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Expected dividend rate $ 0.26 $ 0.22
Expected volatility 30.81% 42.38%
Risk-free interest rate 1.90% 2.02%
Expected life 5 years 8 years
2007 Long-Term Incentive Plan Employees [Member]    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Expected dividend rate $ 0.26 $ 0.22
Expected volatility 30.86% 42.34%
Risk-free interest rate 1.91% 2.03%
Expected life 5 years 8 years