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Indebtedness - Additional Information (Detail) - USD ($)
May 09, 2019
Apr. 30, 2019
Jun. 30, 2019
Dec. 31, 2018
Debt Instrument [Line Items]        
Deferred financing costs     $ 6,139,000 $ 5,927,000
Mortgages-Fixed Rate        
Debt Instrument [Line Items]        
Mortgage loan related to property disposition   $ 18,850,000    
Unsecured Revolving Line of Credit        
Debt Instrument [Line Items]        
Credit facility, revolving line of credit $ 350,000,000      
Maturity date May 09, 2023      
Maturity term description option to extend the revolving commitment for two additional 6-month periods under certain circumstances, including the payment of an extension fee      
Deferred financing costs $ 1,129,000      
Unsecured Revolving Line of Credit | LIBOR        
Debt Instrument [Line Items]        
Debt interest rate 1.55%      
Unsecured Revolving Line of Credit | Minimum | 1-month LIBOR Rate        
Debt Instrument [Line Items]        
Debt interest rate 1.25%      
Unsecured Revolving Line of Credit | Minimum | Base Rate        
Debt Instrument [Line Items]        
Debt interest rate 2.50%      
Unsecured Revolving Line of Credit | Maximum        
Debt Instrument [Line Items]        
Credit facility borrowing capacity $ 600,000,000      
Unsecured Revolving Line of Credit | Maximum | 1-month LIBOR Rate        
Debt Instrument [Line Items]        
Debt interest rate 2.00%      
Unsecured Revolving Line of Credit | Maximum | Base Rate        
Debt Instrument [Line Items]        
Debt interest rate 1.00%