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Share-Based Incentive Compensation Plans - Fair Value Assumptions (Details) - $ / shares
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Stock options    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Expected volatility 28.60%  
Expected term (in years) 6 years 7 days  
Strike price (usd per share) $ 37.60  
Risk-free interest rate 2.10%  
Expected dividend yield 0.11%  
Weighted average estimated fair value (usd per share) $ 11.89  
Total Shareholder Return    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Expected volatility 26.67% 24.37%
Average expected volatility of peer companies 27.43% 25.63%
Expected term (in years) 2 years 10 months 10 days 2 years 9 months 26 days
Risk-free interest rate 1.45% 1.05%
Expected dividend yield 0.00% 0.00%
Average correlation coefficient of peer companies 68.00% 61.00%