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Stock-Based Employee Compensation (Monte Carlo Assumptions) (Details) - Market-Based Stock Units - $ / shares
1 Months Ended
May 15, 2017
Jun. 15, 2016
Jun. 15, 2015
Jun. 15, 2014
May 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Estimated fair value (in dollars per share) $ 27.65 $ 28.01 $ 33.08 $ 21.00  
Expected volatility (percent) 43.36% 46.90% 41.22% 34.60%  
Expected term (in years) 2 years 10 months 17 days 1 year 9 months 18 days 1 year 9 months 18 days 1 year 9 months 18 days 3 years
Risk-free interest rate (percent) 1.47% 0.70% 0.65% 0.38%