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Significant Accounting Policies - Estimated Fair Value of Assets and Liability (Detail) - Fair Value, Measurements, Recurring - USD ($) $ in Thousands | Dec. 31, 2024 | Dec. 31, 2023
--- | --- | ---
Asset: |  |
Asset, fair value | $ 247,178 | $ 235,380
Level 1 |  |
Asset: |  |
Asset, fair value | 242,178 | 223,218
Level 2 |  |
Asset: |  |
Asset, fair value | 5,000 | 12,162
Money Market Fund |  |
Asset: |  |
Asset, fair value | 67,456 | 99,226
Money Market Fund | Level 1 |  |
Asset: |  |
Asset, fair value | 67,456 | 99,226
U.S. Treasury Shares |  |
Asset: |  |
Asset, fair value | 174,722 | 123,992
U.S. Treasury Shares | Level 1 |  |
Asset: |  |
Asset, fair value | 174,722 | 123,992
Agency Securities |  |
Asset: |  |
Asset, fair value |  | 8,912
Agency Securities | Level 2 |  |
Asset: |  |
Asset, fair value |  | 8,912
Repo Securities |  |
Asset: |  |
Asset, fair value | 5,000 | 3,250
Repo Securities | Level 2 |  |
Asset: |  |
Asset, fair value | $ 5,000 | $ 3,250

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