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Stock Options - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands | 1 Months Ended | 12 Months Ended
--- | --- | ---
Jan. 31, 2021 | Jun. 30, 2017 | Dec. 31, 2021 | Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2017
Share-based awards |  |  |  |  |  |
Number of shares outstanding (in shares) |  |  | 8,342,429 | 6,112,948 |  |
Options granted (in shares) |  |  | 3,308,220 |  |  |
Weighted-average grant date fair value of options granted (in dollars per share) |  |  | $ 11.71 | $ 7.99 | $ 2.47 |
Intrinsic value of options exercised |  |  | $ 4,299 | $ 11,147 | $ 202 |
Cash received from the exercise of stock options (in dollars) |  |  | $ 1,837 | $ 3,138 | $ 175 |
Expected dividend yield |  |  | 0.00% | 0.00% | 0.00% |
Number of shares reserved for future issuance (in shares) |  |  | 9,199,512 | 6,869,189 |  |
Employee stock purchase plan |  |  |  |  |  |
Share-based awards |  |  |  |  |  |
Number of shares available for future issuance (in shares) |  |  | 566,565 |  |  |
Number of shares reserved for future issuance (in shares) |  |  |  |  |  | 225,000
Purchase of common stock under ESPP (in shares) |  |  | 78,253 | 80,267 |  |
Stock options |  |  |  |  |  |
Share-based awards |  |  |  |  |  |
Unrecognized stock compensation cost |  |  | $ 38,958 |  |  |
Weighted-average amortization period of unrecognized stock compensation cost |  |  | 2 years 7 months 6 days |  |  |
Unvested restricted stock units |  |  |  |  |  |
Share-based awards |  |  |  |  |  |
Fair value of RSUs vested |  |  | $ 5,790 | $ 0 | $ 0 |
Unrecognized stock compensation cost |  |  | $ 9,929 |  |  |
Weighted-average amortization period of unrecognized stock compensation cost |  |  | 2 years 9 months 18 days |  |  |
Unvested restricted stock units | Maximum |  |  |  |  |  |
Share-based awards |  |  |  |  |  |
Vesting period |  |  | 4 years |  |  |
Unvested restricted stock units | Minimum |  |  |  |  |  |
Share-based awards |  |  |  |  |  |
Vesting period |  |  | 1 year |  |  |
2007 Plan |  |  |  |  |  |
Share-based awards |  |  |  |  |  |
Number of shares outstanding (in shares) |  | 3,141,625 |  |  |  |
2017 Plan |  |  |  |  |  |
Share-based awards |  |  |  |  |  |
Number of shares authorized (in shares) |  | 2,255,000 |  |  |  |
Cumulative annual increase in number of shares issuable, percentage |  | 4.00% |  |  |  |
Additional shares authorized (in shares) | 2,753,651 |  |  |  |  |
Number of shares available for future issuance (in shares) |  |  | 1,308,183 |  |  |
Options granted (in shares) |  |  | 2,870,720 |  |  |
2017 Plan | Maximum |  |  |  |  |  |
Share-based awards |  |  |  |  |  |
Expiration period |  |  | 10 years |  |  |
2017 Plan | Stock options |  |  |  |  |  |
Share-based awards |  |  |  |  |  |
Vesting period |  |  | 4 years |  |  |
2017 Plan | Unvested restricted stock units |  |  |  |  |  |
Share-based awards |  |  |  |  |  |
RSUs granted (in shares) |  |  | 715,716 |  |  |
Inducement Award Program |  |  |  |  |  |
Share-based awards |  |  |  |  |  |
Number of shares outstanding (in shares) |  |  | 757,500 |  |  |
2017 ESPP | Employee stock purchase plan |  |  |  |  |  |
Share-based awards |  |  |  |  |  |
Cumulative annual increase in number of shares issuable, percentage |  |  |  |  |  | 1.00%
2017 ESPP | Employee stock purchase plan | Common Stock |  |  |  |  |  |
Share-based awards |  |  |  |  |  |
Maximum annual increase (in shares) |  |  |  |  |  | 450,000
2017 ESPP | Employee stock purchase plan | Maximum |  |  |  |  |  |
Share-based awards |  |  |  |  |  |
Number of shares authorized (in shares) |  |  |  |  |  | 4,725,000

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