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Stock Based Compensation - Compensation costs (Details) - USD ($) $ in Thousands | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2024 | Sep. 30, 2023 | Sep. 30, 2024 | Sep. 30, 2023
Compensation cost |  |  |  |
Equity-based compensation cost | $ 3,073 | $ 3,302 | $ 8,987 | $ 8,447
Unrecognized compensation costs related to restricted stock units | 22,407 | 31,843 | 22,407 | 31,843
Restricted stock units (RSUs) |  |  |  |
Compensation cost |  |  |  |
Equity-based compensation cost | 1,499 | 1,248 | 4,107 | 2,839
Employee stock option |  |  |  |
Compensation cost |  |  |  |
Equity-based compensation cost | 1,529 | 2,012 | 4,756 | 5,486
ESPP |  |  |  |
Compensation cost |  |  |  |
Equity-based compensation cost | $ 45 | $ 42 | $ 124 | $ 122

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