Annual report pursuant to Section 13 and 15(d)

Stock Based Compensation - Assumptions for LTIP Awards (Details)

v3.19.3.a.u2
Stock Based Compensation - Assumptions for LTIP Awards (Details) - LTIP - $ / shares
12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Expected volatility (percent) [1] 18.10% 17.90%  
Expected volatility, minimum (percent) [2]   18.50%  
Expected volatility, maximum (percent) [2]   18.70%  
Risk-free interest rate (percent) [1] 2.40% 2.40% 1.50%
Share price at grant date (in dollars per share) $ 23.00 $ 26.06  
Minimum      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Expected term (in years) [3] 3 years 3 years 3 years
Share price at grant date (in dollars per share)   $ 30.84  
Maximum      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Expected term (in years) [3] 4 years 4 years 4 years
Share price at grant date (in dollars per share)   $ 32.69  
[1] Risk-free interest rate based on U.S. treasury constant maturity bonds on the measurement date with a maturity equal to the market condition performance period.
[2] Expected volatility based upon historical volatility of our daily closing share price.
[3] Expected term based on the market condition performance period.