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Real Estate Securities - Trading Securities by Collateral Type (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022	Dec. 31, 2022
Debt and Equity Securities, FV-NI [Line Items]
Real estate securities, at fair value	$ 69,323		$ 69,323		$ 108,329
Unpaid principal balance	76,512		76,512		215,592
Fair value of securities acquired	6,183	$ 0	7,883	$ 5,006
Fair value of securities sold	51,578	23,329	55,087	23,329
Net market valuation gains (losses) recorded	6,495	$ (16,042)	8,456	$ (17,498)
Senior Securities
Debt and Equity Securities, FV-NI [Line Items]
Real estate securities, at fair value	38,064		38,064		28,867
Unpaid principal balance	0		0		0
Subordinate
Debt and Equity Securities, FV-NI [Line Items]
Real estate securities, at fair value	31,259		31,259		79,462
Unpaid principal balance	76,512		76,512		215,592
Interest Only Senior Trading Securities \| Senior Securities
Debt and Equity Securities, FV-NI [Line Items]
Real estate securities, at fair value	38,064		38,064		28,867
Interest Only Senior Trading Securities \| Senior Securities \| Sequoia
Debt and Equity Securities, FV-NI [Line Items]
Real estate securities, at fair value	26,000		26,000		26,000
RPL securities \| Subordinate
Debt and Equity Securities, FV-NI [Line Items]
Real estate securities, at fair value	11,884		11,884		29,002
Consolidated Agency multifamily loans, at fair value \| Subordinate
Debt and Equity Securities, FV-NI [Line Items]
Real estate securities, at fair value	4,993		4,993		5,027
Other third-party residential securities \| Subordinate
Debt and Equity Securities, FV-NI [Line Items]
Real estate securities, at fair value	$ 14,382		$ 14,382		$ 45,433