Asset Acquisitions and Dispositions - Net gain (loss) on real estate and mortgage loans (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Real Estate And Mortgage Loans On Real Estate Acquisitions And Disposals [Abstract]
Conversion of mortgage loans to REO, net	$ 0	$ 17	$ 0	$ 769
Change in fair value of mortgage loans, net	0	(81)	0	211
Net realized loss on mortgage loans	0	(1,671)	0	(944)
Net realized gain on sales of real estate	176	2,089	1,546	12,937
Net gain on real estate and mortgage loans	$ 176	$ 354	$ 1,546	$ 12,973