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Stock-Based Compensation - Assumptions (Details) - Stock options
3 Months Ended
Mar. 31, 2017
Mar. 31, 2016
Stock-Based Compensation    
Risk-free interest rates, minimum (as a percent) 2.02% 1.32%
Risk-free interest rates, maximum (as a percent) 2.09% 2.05%
Expected life 5 years 6 months 22 days  
Volatility, minimum (as a percent) 33.97% 34.39%
Volatility, maximum (as a percent) 34.13% 41.60%
Minimum    
Stock-Based Compensation    
Vesting period 3 years  
Expected life   5 years 9 months
Expected dividend yield (as a percent) 0.67% 0.00%
Maximum    
Stock-Based Compensation    
Vesting period 4 years  
Expected life   7 years 7 days
Expected dividend yield (as a percent) 0.74% 0.63%