Debt - Related Party Mortgage Loans Payable (Details)
$ in Thousands
6 Months Ended
Jun. 30, 2019
USD ($)
Property
loan
Dec. 31, 2018
USD ($)
Debt Instrument [Line Items]    
Outstanding principal $ 2,154,107 $ 2,084,302
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 $ 26,404 $ 27,890
Number of properties agreed to sell | Property 3  
Gross proceeds from sale of properties $ 55,000  
Weighted Average    
Debt Instrument [Line Items]    
Weighted average effective interest rate 4.75%  
Weighted average maturity 5 years 2 months 12 days  
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 8 years 8 months 12 days