Agreements and Transactions with Related Parties - Due from Affiliates (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Due from affiliates
Short-term loans to affiliates, including accrued interest	$ 30,760	$ 47,721
Deferred acquisition fees receivable, including accrued interest	3,000	4,450
Reimbursable costs	2,759	3,129
Asset management fees receivable	1,388	1,267
Accounts receivable	908	1,118
Current acquisition fees receivable	236	131
Due from affiliates	$ 39,051	$ 57,816