Real Estate Securities - Available for Sale Securities by Collateral Type (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Investment Holdings [Line Items]
Available-for-sale	$ 185,198		$ 206,792
Fair value of securities acquired	10,000	$ 1,078
Fair value of securities sold	0	2,200
Principal balance of securities called	14,486	$ 3,444
Subordinate
Investment Holdings [Line Items]
Available-for-sale	185,198		206,792
Sequoia securities \| Subordinate
Investment Holdings [Line Items]
Available-for-sale	108,768		127,542
Multifamily loans, held-for-investment, at fair value \| Subordinate
Investment Holdings [Line Items]
Available-for-sale	15,316		22,166
Other third-party residential securities \| Subordinate
Investment Holdings [Line Items]
Available-for-sale	$ 61,114		$ 57,084

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