Related-Party Transactions - Summary of related-party transactions (Details) - AAMC - Affiliated entity - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Base management fees
Related Party Transaction [Line Items]
Related party expenses	$ 3,584	$ 3,584	$ 10,752	$ 10,686
Conversion fees
Related Party Transaction [Line Items]
Related party expenses	0	0	0	29
Expense reimbursements
Related Party Transaction [Line Items]
Related party expenses	626	250	1,707	920
Termination fee
Related Party Transaction [Line Items]
Related party expenses	$ 46,000	$ 0	$ 46,000	$ 0