Related Party Transactions and Arrangements - Property Management and Servicing Agreement (Details) - USD ($)
$ in Thousands
3 Months Ended 9 Months Ended
May 20, 2014
Sep. 30, 2019
Sep. 30, 2018
Sep. 30, 2019
Sep. 30, 2018
Dec. 31, 2018
Related Party Transaction [Line Items]            
Related party fee income   $ 54,795 $ 6,750 $ 68,971 $ 8,969  
Affiliated Entity | Property Management            
Related Party Transaction [Line Items]            
Annual management fees rate 0.25%          
Related party fee income   1,300 1,600 4,300 2,100  
Affiliated Entity | Special Servicing Fees            
Related Party Transaction [Line Items]            
Annual management fees rate 0.75%          
Related party fee income   $ 400 $ 190 $ 1,200 $ 242  
Affiliated Entity | Property Management and Servicing Agreement            
Related Party Transaction [Line Items]            
Due from related parties           $ 500