Debt - Revolving Credit Facilities - Narrative (Details) - USD ($)
 3 Months Ended
Mar. 31, 2017
Jun. 30, 2016
Dec. 31, 2016
Aug. 18, 2016
Apr. 27, 2016
Mar. 31, 2015
Line of Credit Facility [Line Items]            
Total debt, gross $ 3,742,866,000   $ 3,754,633,000      
Unsecured Debt            
Line of Credit Facility [Line Items]            
Line of credit facility, maximum borrowing capacity         $ 800,000,000 $ 600,000,000
Line of credit facility, accordion feature, increase limit           1,000,000,000
Commitment fee (as a percent) 0.25%          
Origination costs $ 4,800,000     $ 3,200,000    
Letters of credit issued 0          
Line of credit facility remaining borrowing capacity $ 671,000,000          
Unsecured Debt | Minimum            
Line of Credit Facility [Line Items]            
Commitment fee (as a percent)   0.125%        
Unsecured Debt | Maximum            
Line of Credit Facility [Line Items]            
Commitment fee (as a percent)   0.30%        
Unsecured Debt | LIBOR            
Line of Credit Facility [Line Items]            
Basis spread on variable rate (as a percent) 1.25%          
Unsecured Debt | LIBOR | Minimum            
Line of Credit Facility [Line Items]            
Basis spread on variable rate (as a percent)   0.875%        
Unsecured Debt | LIBOR | Maximum            
Line of Credit Facility [Line Items]            
Basis spread on variable rate (as a percent)   1.55%        
Unsecured Debt | Base Rate | Minimum            
Line of Credit Facility [Line Items]            
Basis spread on variable rate (as a percent)   0.00%        
Unsecured Debt | Base Rate | Maximum            
Line of Credit Facility [Line Items]            
Basis spread on variable rate (as a percent)   0.55%        
Unsecured Debt | Swing-line Loans            
Line of Credit Facility [Line Items]            
Line of credit facility, maximum borrowing capacity           50,000,000
Unsecured Debt | Letters of Credit            
Line of Credit Facility [Line Items]            
Line of credit facility, maximum borrowing capacity           $ 60,000,000
2015 Credit Facility            
Line of Credit Facility [Line Items]            
Total debt, gross $ 129,000,000   86,000,000      
Deferred Costs And Other Assets | Revolving Line of Credit            
Line of Credit Facility [Line Items]            
Unamortized deferred financing costs $ 2,600,000   $ 2,900,000