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Stock Based Compensation - Valuation Assumptions (Details) - New LTIP [Member] - $ / shares
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Apr. 23, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Fair value assumptions, expected volatility rate   23.20%  
Fair value assumptions, risk free interest rate   0.80%  
Closing share price, date of grant     $ 24.08
Minimum [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Fair value assumptions, expected term 3 years 3 years  
Fair value assumptions, expected volatility rate 17.20%    
Fair value assumptions, risk free interest rate 1.00%    
Closing share price, date of grant $ 27.66    
Maximum [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Fair value assumptions, expected term 4 years 4 years  
Fair value assumptions, expected volatility rate 17.50%    
Fair value assumptions, risk free interest rate 1.10%    
Closing share price, date of grant $ 27.76