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Significant Accounting Policies - Estimated Fair Value of Assets and Liability (Detail) - Fair Value, Measurements, Recurring - USD ($) $ in Thousands | Sep. 30, 2022 | Dec. 31, 2021
--- | --- | ---
Asset: |  |
Asset, fair value | $ 195,933 | $ 374,911
Money Market Fund |  |
Asset: |  |
Asset, fair value | 117,301 | 95,063
U.S. Treasury Shares |  |
Asset: |  |
Asset, fair value | 8,059 | 23,219
Corporate Bonds |  |
Asset: |  |
Asset, fair value | 35,880 | 83,587
Commercial Paper |  |
Asset: |  |
Asset, fair value | 21,519 | 121,773
Repo Securities |  |
Asset: |  |
Asset, fair value | 3,250 | 8,000
Asset Backed Securities |  |
Asset: |  |
Asset, fair value | 2,237 | 8,816
Certificates of Deposit |  |
Asset: |  |
Asset, fair value | 6,297 | 21,553
Non-US Government |  |
Asset: |  |
Asset, fair value | 1,390 | 12,900
Level 1 |  |
Asset: |  |
Asset, fair value | 125,360 | 118,282
Level 1 | Money Market Fund |  |
Asset: |  |
Asset, fair value | 117,301 | 95,063
Level 1 | U.S. Treasury Shares |  |
Asset: |  |
Asset, fair value | 8,059 | 23,219
Level 2 |  |
Asset: |  |
Asset, fair value | 70,573 | 256,629
Level 2 | Corporate Bonds |  |
Asset: |  |
Asset, fair value | 35,880 | 83,587
Level 2 | Commercial Paper |  |
Asset: |  |
Asset, fair value | 21,519 | 121,773
Level 2 | Repo Securities |  |
Asset: |  |
Asset, fair value | 3,250 | 8,000
Level 2 | Asset Backed Securities |  |
Asset: |  |
Asset, fair value | 2,237 | 8,816
Level 2 | Certificates of Deposit |  |
Asset: |  |
Asset, fair value | 6,297 | 21,553
Level 2 | Non-US Government |  |
Asset: |  |
Asset, fair value | $ 1,390 | $ 12,900

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