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Stock-based Compensation - Additional Infomation (Details) - USD ($) $ / shares in Units, $ in Thousands | 1 Months Ended | 3 Months Ended | 9 Months Ended | 12 Months Ended |  |
--- | --- | --- | --- | --- | --- | ---
Sep. 30, 2021 | Sep. 30, 2021 | Sep. 30, 2020 | Sep. 30, 2021 | Sep. 30, 2020 | Dec. 31, 2020 | Jun. 30, 2021 | Jun. 16, 2021
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |
Common stock, shares, issued | 239,789,000 | 239,789,000 |  | 239,789,000 |  | 15,570,000 |  |
Weighted average grant date fair value |  |  |  | $ 6.55 | $ 3.21 |  |  |
Share Based Compensation Expense |  | $ 13,042 | $ 9,748 | $ 41,023 | $ 20,290 |  |  |
Total stock-based compensation cost related to unvested awards not yet recognized | $ 122,500 | $ 122,500 |  | $ 122,500 |  |  |  |
Expected weighted-average period compensation cost to be recognized |  |  |  | 2 years 5 months 15 days |  |  |  |
IPO [Member] |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |
Share-based Payment Arrangement, Accelerated Cost |  |  |  | $ 2,600 |  |  |  |
2021 Plan |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |
Vesting period |  |  |  | 4 years |  |  |  |
Common shares reserved for future issuance | 24,900,000 | 24,900,000 |  | 24,900,000 |  |  |  | 26,662,087
Percentage of Common shares reserved for future issuance increase |  |  |  | 5.00% |  |  |  |
2021 Plan | Maximum [Member] |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |
Option expiration period |  |  |  | 10 years |  |  |  |
2021 ESPP |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |
Common stock, shares, issued | 0 | 0 |  | 0 |  |  |  |
Common shares reserved for future issuance |  |  |  |  |  |  | 2,470,000 |
Percentage of Common shares reserved for future issuance increase |  |  |  |  |  | 1.00% |  |
Share-based compensation arrangement by share-based payment award, other share increase (decrease) |  |  |  | 4,940,000 |  |  |  |
Percentage of Purchase of shares at fair value | 85.00% |  |  |  |  |  |  |
2021 ESPP | Maximum [Member] |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |
Maximum offering period | 27 months |  |  |  |  |  |  |
Purchase of common stock at discount | 15.00% | 15.00% |  | 15.00% |  |  |  |

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