Debt - Related Party Mortgage Loans Payable (Details)
$ in Thousands
3 Months Ended
Mar. 31, 2019
USD ($)
Property
loan
Dec. 31, 2018
USD ($)
Debt Instrument [Line Items]    
Outstanding principal $ 2,131,480 $ 2,084,302
Related party notes payable    
Debt Instrument [Line Items]    
Outstanding principal $ 27,148 $ 27,890
Related party notes payable | Affiliated Entity | Mortgage loans payable    
Debt Instrument [Line Items]    
Number of mortgage loans with related party | loan 4  
Number of properties with related party | Property 6  
Outstanding principal $ 27,100  
Weighted Average    
Debt Instrument [Line Items]    
Weighted average effective interest rate 5.13%  
Weighted average maturity 3 years 9 months  
Weighted Average | Related party notes payable    
Debt Instrument [Line Items]    
Weighted average effective interest rate 1.00%  
Weighted average maturity 9 years  
Weighted Average | Related party notes payable | Affiliated Entity | Mortgage loans payable    
Debt Instrument [Line Items]    
Weighted average effective interest rate 1.00%  
Weighted average maturity 9 years