Related Party Transactions and Arrangements - Asset Management Agreement (Details) - USD ($)
$ in Thousands
3 Months Ended 6 Months Ended
May 31, 2018
Jun. 30, 2018
Jun. 30, 2017
Jun. 30, 2018
Jun. 30, 2017
Related Party Transaction [Line Items]          
Related party fee income   $ 2,219 $ 0 $ 2,219 $ 0
Affiliated entity | Asset management agreement          
Related Party Transaction [Line Items]          
Annual management revenue in related party transaction $ 20,000        
Related party fee income   1,700   1,700  
Due from related parties   $ 1,700   $ 1,700