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Real Estate Securities - Additional Information (Details) $ in Thousands | Mar. 31, 2021 USD ($) investment | Dec. 31, 2020 USD ($) investment
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Investment Holdings [Line Items] |  |
Number of AFS securities (in investments) | investment | 93 | 96
Number of securities in unrealized loss position | investment | 4 | 5
Number of securities in a continuous unrealized loss position for twelve consecutive months or longer (in investments) | investment | 3 | 0
Gross unrealized losses | $ 252 | $ 1,047
CECL credit allowance | 13 | 388
Residential |  |
Investment Holdings [Line Items] |  |
AFS securities, contractual maturities, less than five years | 35,000 |
Marketable securities, due from five to ten years | 4,000 |
CECL credit allowance | $ 44,947 | $ 44,967

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