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Share-Based Compensation - 2016 and 2015 Performance-Based RSU Grants (Details) - USD ($)
$ / shares in Units, $ in Millions
1 Months Ended 12 Months Ended
Jan. 28, 2016
Jan. 27, 2015
Apr. 04, 2013
Feb. 28, 2012
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]              
Fair value per share on valuation date           $ 78.55  
Employee Stock Option [Member]              
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]              
Expected share price volatility       33.00%      
Risk-free interest rate       1.35%      
Remaining expected life       6 years 6 months      
2016 Performance Based RSUs [Member]              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Fair value RSUs granted $ 9.6            
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]              
Fair value per share on valuation date         $ 57.08    
Expected share price volatility         26.00%    
Risk-free interest rate         1.13%    
Remaining expected life         2 years 11 months    
Market measure-based Restricted Stock Units (RSUs) [Member]              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Share-based compensation arrangement by share-based payment award, equity instruments other than options, grants in period 168,077 127,657          
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]              
Fair value per share on valuation date         $ 57.36 $ 79.25 $ 64.86
Expected share price volatility           20.00%  
Risk-free interest rate           0.92%  
Remaining expected life           2 years 11 months  
Market Measure-Based RSU Estimate of Probable [Member] | Market measure-based Restricted Stock Units (RSUs) [Member]              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Estimated RSUs earned based on FFO 241,438 185,510          
Chief Executive Officer [Member] | Executive officer share-based compensation programs [Member] | Market measure-based Restricted Stock Units (RSUs) [Member]              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Fair value RSUs granted     $ 10.1