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Equity and Capital (Details) - USD ($)
$ / shares in Units, $ in Millions
3 Months Ended 9 Months Ended
Sep. 30, 2017
Sep. 30, 2016
Sep. 30, 2017
Sep. 30, 2016
Dec. 31, 2016
Noncontrolling Interest [Line Items]          
Common stock authorized for sale under the ATM     $ 400.0    
Common stock remained available for issuance under the ATM $ 400.0   $ 400.0    
Dividends, per common share $ 0.26 $ 0.245 $ 0.78 $ 0.735  
Series A Redeemable Preferred Stock          
Noncontrolling Interest [Line Items]          
Stock redeemed, shares     125    
Redemption price per share $ 10,000   $ 10,000    
Parent Company | Operating Partnership          
Noncontrolling Interest [Line Items]          
Ownership percentage 100.00%   100.00%    
OP Units          
Noncontrolling Interest [Line Items]          
Shares exchanged     400,000    
Accounts Payable and Accrued Liabilities          
Noncontrolling Interest [Line Items]          
Dividends payable $ 81.1   $ 81.1   $ 80.6
Common Stock          
Noncontrolling Interest [Line Items]          
Stock repurchased during period, shares     100,000.0 100,000.0  
Shares exchanged     403,000 4,976,000