Real Estate Securities - Trading Securities by Collateral Type (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Investment Holdings [Line Items]
Real estate securities	$ 173,684		$ 170,619
Unpaid principal balance	234,732		235,306
Principal balance of securities acquired (1)	0	$ 15,880
Principal balance of securities sold (1)	0	34,743
Net market valuation gains (losses) recorded	(1,456)	21,349
Securities bought and sold during the same quarter	0	$ 2,000
Senior IO Securities
Investment Holdings [Line Items]
Real estate securities	34,206		21,787
Unpaid principal balance	0		0
Subordinate
Investment Holdings [Line Items]
Real estate securities	139,478		148,832
Unpaid principal balance	234,732		235,306
Interest Only Senior Trading Securities \| Senior IO Securities
Investment Holdings [Line Items]
Real estate securities	34,206		21,787
Interest Only Senior Trading Securities \| Senior IO Securities \| Sequoia
Investment Holdings [Line Items]
Real estate securities	20,000		15,000
RPL securities \| Subordinate
Investment Holdings [Line Items]
Real estate securities	63,164		65,140
Multifamily loans, held-for-investment, at fair value \| Subordinate
Investment Holdings [Line Items]
Real estate securities	9,008		10,549
Other third-party residential securities \| Subordinate
Investment Holdings [Line Items]
Real estate securities	$ 67,306		$ 73,143

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Amount of increase (decrease) of investment in debt and equity securities, measured at fair value with changes in fair value recognized in net income.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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For investments which are quantified by principal amount, the principle balance held at close of period.

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The cash outflow to acquire securities classified as trading securities and held for investment purposes. Excludes payments for trading securities purchased and held principally for the purpose of selling them in the near term (thus held for only a short period of time).

+ References

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The cash inflow associated with the sale of securities classified as trading securities and held for investment purposes. Excludes proceeds from trading securities purchased and held principally for the purpose of selling them in the near term (thus held for only a short period of time).

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Amount of investment in debt security measured at fair value with change in fair value recognized in net income (trading) and investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

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