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Stock Option Plan - Narrative (Details) - USD ($) | 3 Months Ended | 12 Months Ended |  |
--- | --- | --- | --- | ---
Dec. 31, 2019 | Dec. 31, 2019 | Dec. 31, 2018 | Jan. 01, 2020 | Jul. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |
Employee options, weighted-average grant date fair value per share (in dollars per share) |  | $ 7.79 | $ 0.17 |  |
Common stock, fair value per share (in dollars per share) | $ 25.40 | $ 25.40 | $ 9.92 |  |
Stock options, unrecognized compensation cost | $ 5,600,000 | $ 5,600,000 |  |  |
Stock options, cost not yet recognized, remaining weighted average vesting period |  | 3 years 3 months 18 days |  |  |
Stock-based compensation expense |  | $ 572,000 | $ 114,000 |  |
Stock options |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |
Stock options, expiration period |  | 10 years |  |  |
Stock options, vesting period |  | 4 years |  |  |
Employee Stock Purchase Plan |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |
Shares reserved for issuance under Stock Option Plan | 120,000 | 120,000 |  |  |
Annual percentage increase in shares available for issuance under the Plan | 100.00% | 100.00% |  |  |
Maximum Employee payroll deduction percentage | 2000.00% | 2000.00% |  |  |
Stock-based compensation expense | $ 0 | $ 0 |  |  |
Employee Stock Purchase Plan | Subsequent Event |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |
Increase (decrease) in number of shares authorized (in shares) |  |  |  | 125,610 |
2013 Stock Option Plan | Stock options |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |
Shares reserved for issuance under Stock Option Plan | 669,806 | 669,806 |  |  | 1,663,681
2019 Incentive Award Plan | Stock options |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |
Shares reserved for issuance under Stock Option Plan | 2,011,832 | 2,011,832 |  |  |
Annual percentage increase in shares available for issuance under the Plan | 4.00% | 4.00% |  |  |
Shares that remain available for future awards | 1,283,996 | 1,283,996 |  |  |
2019 Incentive Award Plan | Stock options | Subsequent Event |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |
Increase (decrease) in number of shares authorized (in shares) |  |  |  | 502,440 |

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- Definition The highest percentage of annual salary that an employee is permitted to utilize with respect to the plan. + 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 -URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901 + Details
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- Definition The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable. + 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 -URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901 + Details
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