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Stock-Based Compensation and Warrants - Stock incentive plan and other information (Details) - USD ($) |  | 1 Months Ended | 12 Months Ended |  |  |  |  |  |  |
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Nov. 18, 2016 | Sep. 30, 2021 | Mar. 20, 2007 | Dec. 31, 2021 | Dec. 31, 2020 | Nov. 16, 2020 | Sep. 17, 2020 | Dec. 31, 2019 | Oct. 15, 2018 | Dec. 26, 2017 | Nov. 08, 2016 | Nov. 02, 2010
Share-based Compensation Arrangement by Share-based Payment Award |  |  |  |  |  |  |  |  |  |  |  |
Employee Service Share-based Compensation, Nonvested Awards, Compensation Not yet Recognized, Stock Options |  |  |  | $ 771,000 |  |  |  |  |  |  |  |
Proceeds from Stock Options Exercised |  |  |  | 0 | $ 0 |  |  |  |  |  |  |
Exercise price per warrant |  |  |  |  |  | $ 1.38 |  |  | $ 1.38 |  |  |
Warrants Not Settleable in Cash, Fair Value Disclosure |  |  |  |  |  |  |  |  |  | $ 9,000 |  |
IPO [Member] |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award |  |  |  |  |  |  |  |  |  |  |  |
Stock Issued During Period, Shares, New Issues | 714,286 |  |  |  |  |  |  |  |  |  |  |
Class of Warrant or Right, Number of Securities Called by Warrants or Rights |  |  |  |  |  |  |  |  |  |  | 1,428,571 |
Shares Issued, Price Per Share | $ 35.00 |  |  |  |  |  |  |  |  |  |  |
Warrants Not Settleable in Cash, Fair Value Disclosure |  |  |  |  |  | $ 15,700,000 |  | $ 100,000,000 |  |  |  |
Series B Warrants [Member] | IPO [Member] |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award |  |  |  |  |  |  |  |  |  |  |  |
Exercise price per warrant | $ 60.20 |  |  |  |  |  |  |  |  |  |  |
General and Administrative Expenses and Research and Development Expense [Member] | Employees [Member] |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award |  |  |  |  |  |  |  |  |  |  |  |
Allocated Share-based Compensation Expense |  |  |  | $ 204,000 | $ 213,000 |  |  |  |  |  |  |
Employees And Directors [Member] |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross |  |  |  | 2,260,000 | 1,540,000 |  |  |  |  |  |  |
Consultant [Member] | General and Administrative Expenses and Research and Development Expense [Member] |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award |  |  |  |  |  |  |  |  |  |  |  |
Allocated Share-based Compensation Expense |  |  |  | $ 212,000 | $ 137,000 |  |  |  |  |  |  |
Employees | General and Administrative Expenses and Research and Development Expense [Member] |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award |  |  |  |  |  |  |  |  |  |  |  |
Allocated Share-based Compensation Expense |  |  |  | $ 500,000 | $ 400,000 |  |  |  |  |  |  |
2007 Stock Plan [Member] |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number |  |  | 71,429 | 5,145 |  |  |  |  |  |  |  |
2007 Stock Plan [Member] | Maximum |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross |  |  | 7,143 |  |  |  |  |  |  |  |  |
2010 Stock Plan [Member] |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number |  |  |  | 3,800,000 |  |  |  |  |  |  |  | 85,714
Share-based Compensation Arrangement by Share-based Payment Award, Number of shares authorized |  | 4,000,000,000,000 |  |  |  |  |  |  |  |  |  |
2010 Stock Plan [Member] | Board of Directors [Member] |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number |  |  |  | 2,450,130 |  |  |  |  |  |  |  |
2020 Stock Plan [Member] |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number |  |  |  |  |  |  | 4,000,000 |  |  |  |  |

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