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Significant Accounting Policies - Estimated Fair Value of Assets and Liability (Detail) - Fair Value, Measurements, Recurring - USD ($) $ in Thousands | Jun. 30, 2022 | Dec. 31, 2021
--- | --- | ---
Asset: |  |
Asset, fair value | $ 234,914 | $ 374,911
Money Market Fund |  |
Asset: |  |
Asset, fair value | 123,455 | 95,063
U.S. Treasury Shares |  |
Asset: |  |
Asset, fair value | 3,112 | 23,219
Corporate Bonds |  |
Asset: |  |
Asset, fair value | 47,387 | 83,587
Commercial Paper |  |
Asset: |  |
Asset, fair value | 26,148 | 121,773
Repo Securities |  |
Asset: |  |
Asset, fair value | 4,750 | 8,000
Asset Backed Securities |  |
Asset: |  |
Asset, fair value | 4,498 | 8,816
Certificates of Deposit |  |
Asset: |  |
Asset, fair value | 22,119 | 21,553
Non-US Government |  |
Asset: |  |
Asset, fair value | 3,445 | 12,900
Level 1 |  |
Asset: |  |
Asset, fair value | 126,567 | 118,282
Level 1 | Money Market Fund |  |
Asset: |  |
Asset, fair value | 123,455 | 95,063
Level 1 | U.S. Treasury Shares |  |
Asset: |  |
Asset, fair value | 3,112 | 23,219
Level 2 |  |
Asset: |  |
Asset, fair value | 108,347 | 256,629
Level 2 | Corporate Bonds |  |
Asset: |  |
Asset, fair value | 47,387 | 83,587
Level 2 | Commercial Paper |  |
Asset: |  |
Asset, fair value | 26,148 | 121,773
Level 2 | Repo Securities |  |
Asset: |  |
Asset, fair value | 4,750 | 8,000
Level 2 | Asset Backed Securities |  |
Asset: |  |
Asset, fair value | 4,498 | 8,816
Level 2 | Certificates of Deposit |  |
Asset: |  |
Asset, fair value | 22,119 | 21,553
Level 2 | Non-US Government |  |
Asset: |  |
Asset, fair value | $ 3,445 | $ 12,900

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