Real Estate Owned (REO) and Mortgages Payable - Summary of REO, Net (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Real Estate [Abstract]
Holding costs, net of other income	$ (50)	$ (20)	$ (182)	$ (162)
Valuation adjustments	0	261	0	261
REO, net	$ (50)	$ 241	$ (182)	$ 99