Debt - Related Party Mortgage Loans Payable (Details)
3 Months Ended 9 Months Ended
Sep. 30, 2019
USD ($)
Property
loan
Sep. 30, 2019
USD ($)
Property
loan
Sep. 30, 2018
USD ($)
Dec. 31, 2018
USD ($)
Debt Instrument [Line Items]        
Outstanding principal $ 2,106,741,000 $ 2,106,741,000   $ 2,084,302,000
Gain (Loss) on extinguishment of debt $ (5,580,000) $ (11,473,000) $ 27,092,000  
Related party notes payable | Affiliated Entity | Mortgage loans payable        
Debt Instrument [Line Items]        
Number of mortgage loans with related party | loan 4 4    
Number of properties with related party | Property 6 6    
Outstanding principal       $ 27,890,000
Number of properties sold | Property 3 3    
Number of mortgage loans repaid with related party | loan 4 4    
Gain (Loss) on extinguishment of debt   $ 0    
Gross proceeds from sale of properties   $ 55,000,000.0    
Weighted Average        
Debt Instrument [Line Items]        
Weighted average effective interest rate 4.56% 4.56%    
Weighted Average | Related party notes payable | Affiliated Entity | Mortgage loans payable        
Debt Instrument [Line Items]        
Weighted average effective interest rate 0.96% 0.96%   1.00%