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Debt - Narrative (Details)
3 Months Ended
Mar. 31, 2018
USD ($)
extension
instrument
Dec. 31, 2017
USD ($)
Debt Instrument [Line Items]    
Number of lines of unsecured credit (in instruments) | instrument 2  
Unsecured Debt [Member]    
Debt Instrument [Line Items]    
Unamortized discount (premium), net $ 6,600,000 $ 5,200,000
Unamortized debt issuance expense 20,500,000 18,100,000
Line of Credit [Member]    
Debt Instrument [Line Items]    
Aggregate borrowing capacity 1,240,000,000  
Line of Credit [Member] | Unsecured Line of Credit [Member]    
Debt Instrument [Line Items]    
Unamortized debt issuance expense 4,900,000 3,200,000
Unsecured Line of Credit [Member] | Line of Credit [Member]    
Debt Instrument [Line Items]    
Aggregate borrowing capacity $ 1,200,000,000  
Number of extension options (in extensions) | extension 1  
Extension period (in months) 18 months  
Unsecured Line of Credit [Member] | Line of Credit [Member] | London Interbank Offered Rate (LIBOR) [Member]    
Debt Instrument [Line Items]    
Basis spread on variable rate 0.875%  
Unsecured Line of Credit [Member] | Line of Credit Working Capital [Member]    
Debt Instrument [Line Items]    
Aggregate borrowing capacity $ 35,000,000  
Unsecured Line of Credit [Member] | Line of Credit Working Capital [Member] | London Interbank Offered Rate (LIBOR) [Member]    
Debt Instrument [Line Items]    
Basis spread on variable rate 0.875%  
Mortgage notes payable, net [Member]    
Debt Instrument [Line Items]    
Unamortized discount (premium), net $ (29,200,000) (33,200,000)
Unamortized debt issuance expense $ 4,900,000 $ 5,400,000