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Stock-Based Compensation Plans Stock-Based Compensation Plans (Details 3) - Performance Shares
3 Months Ended 6 Months Ended
Jun. 30, 2017
$ / shares
Jun. 30, 2017
$ / shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Dividend yield (as a percent)   3.20%
Estimated volatility, Minimum (as a percent) 15.30%  
Estimated volatility, Maximum (as a percent) 19.70%  
Risk-free interest rate, minimum (as a percent) 0.69%  
Risk-free interest rate, maximum (as a percent) 1.61%  
Average estimated fair value (in dollars per share) $ 175.86 $ 175.86
Historical volatility (as a percent)   50.00%
Implied volatility (as a percent)   50.00%