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Equity Incentive Plans - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions |  | 12 Months Ended
--- | --- | ---
Feb. 06, 2019 | Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |
Shares outstanding awarded |  | 8,538,060 | 5,107,329 |
Stock options granted during period |  | 4,194,624 | 5,143,551 | 0
Stock options exercised during the year |  | 419,593 |  |
Restricted Stock |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |
Weighted-average period of cost expects to recognize |  | 2 years 9 months 18 days |  |
Unrecognized compensation costs |  | $ 13.5 |  |
Stock Options |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |
Expected dividend yield |  | 0.00% | 0.00% |
Weighted-average grant date fair value per share |  | $ 13.17 | $ 4.87 |
Aggregate fair value of stock options vested during period |  | $ 7.2 | $ 0.1 |
Aggregate intrinsic value of stock options exercised during period |  | 6.9 |  |
Unrecognized compensation costs |  | $ 61.0 |  |
Weighted-average period of cost expects to recognize |  | 2 years 10 months 24 days |  |
Stock options exercised during the year |  |  | 0 |
2019 Equity Incentive Plan |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |
Number of share reserved for future issuance | 5,750,000 |  |  |
Term of awards | 10 years |  |  |
Percentage of amount increase in outstanding shares | 5.00% |  |  |
Common stock available for issuance |  | 1,751,485 |  |
Shares outstanding awarded |  | 4,003,040 |  |
2019 Employee Stock Purchase Plan |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |
Number of share reserved for future issuance | 700,000 | 700,000 |  |
Term of awards | 10 years |  |  |
Percentage of amount increase in outstanding shares | 1.00% |  |  |
2019 Employee Stock Purchase Plan | Stock-Based Compensation Expense |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |
Unrecognized compensation costs |  | $ 1.3 |  |
Weighted-average period of cost expects to recognize |  | 1 year 1 month 6 days |  |
2019 Employee Stock Purchase Plan | Maximum |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |
Purchase of common stock through payroll deductions, percentage | 20.00% |  |  |
2017 Equity Incentive Plan |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |
Shares outstanding awarded |  | 4,535,020 |  |
2017 Equity Incentive Plan | Restricted Stock |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |
Granted stock awards, Unvested |  | 561,868 |  |

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- Definition Weighted-average period over which cost not yet recognized is expected to be recognized for award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (i) -URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901 + Details
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