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Marketable Securities - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands | Mar. 31, 2019 | Dec. 31, 2018
--- | --- | ---
Investment Holdings [Line Items] |  |
Fair value | $ 23,204 | $ 23,166
Macerich Interest |  |
Investment Holdings [Line Items] |  |
Macerich common shares (shares) | 535,265 | 535,265
Economic basis per share (in usd per share) | $ 56.05 |
Economic cost | $ 30,000 |
Fair value | $ 23,204 | $ 23,166
Closing share price (in usd per share) | $ 43.35 | $ 43.28

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