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Debt - Unsecured Revolving Lines of Credit - Additional Information (Details) - USD ($)
Dec. 31, 2019
Oct. 08, 2019
Dec. 31, 2018
Feb. 20, 2018
Debt Instrument [Line Items]        
Maximum borrowing capacity   $ 750,000.0    
Letters of credit, outstanding amount $ 19,800,000   $ 19,700,000  
Unsecured Debt        
Debt Instrument [Line Items]        
Maximum borrowing capacity   600,000,000.0    
Revolving Credit Facility | Unsecured Debt        
Debt Instrument [Line Items]        
Maximum borrowing capacity   $ 250,000,000.0   $ 150,000,000.0
Core Portfolio | Revolving Credit Facility | Unsecured Debt        
Debt Instrument [Line Items]        
Debt available balance 173,600,000   137,700,000  
Maximum borrowing capacity 250,000,000.0   150,000,000.0  
Credit facility amount outstanding 60,800,000   0.0  
Letters of credit, outstanding amount $ 15,600,000   $ 12,300,000