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Marketable Securities - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands | Sep. 30, 2021 | Dec. 31, 2020
--- | --- | ---
Investment Holdings [Line Items] |  |
Fair value | $ 9,435 | $ 6,024
Macerich |  |
Investment Holdings [Line Items] |  |
Closing share price (in usd per share) | $ 16.71 | $ 10.67
Common Stock |  |
Investment Holdings [Line Items] |  |
Macerich common shares (shares) | 564,612 | 564,612

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