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Stock-Based Compensation - Stock incentive plan and other information (Details) - USD ($) | 3 Months Ended | 6 Months Ended | 12 Months Ended |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
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Jun. 30, 2022 | Jun. 30, 2021 | Jun. 30, 2020 | Jun. 30, 2022 | Jun. 30, 2021 | Jun. 30, 2020 | Dec. 31, 2021 | Dec. 31, 2020 | Sep. 17, 2020 | Sep. 05, 2019 | Sep. 04, 2019 | Sep. 24, 2018 | Sep. 23, 2018 | Sep. 07, 2017 | Sep. 06, 2017 | Aug. 25, 2016 | Aug. 24, 2016 | May 15, 2015 | May 14, 2015 | Oct. 22, 2013 | Oct. 21, 2013 | Nov. 02, 2010 | Mar. 20, 2007
Share-based Compensation Arrangement by Share-based Payment Award |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number |  |  |  |  |  |  | 625,527 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross |  |  |  | 3,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Employee Service Share-based Compensation, Nonvested Awards, Compensation Not yet Recognized, Stock Options | $ 516,000 |  |  | $ 516,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Stock Option [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number | 607,334 |  |  | 607,334 |  |  |  | 399,742 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross |  | 0 |  |  | 0 |  | 226,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
General and Administrative Expense [Member] | Employees [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Allocated Share-based Compensation Expense | $ 39,000 | $ 34,000 |  | $ 78,000 | $ 67,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Research and Development Expenses | Employees [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Allocated Share-based Compensation Expense | 21,000 | 16,000 |  | 41,000 | 31,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Consultant [Member] | General and Administrative Expense [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Allocated Share-based Compensation Expense | 46,000 | $ 49,000 |  | 93,000 | $ 98,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Consultant [Member] | Research and Development Expenses |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Allocated Share-based Compensation Expense | $ 7,000 |  | $ 3,000 | $ 14,000 |  | $ 7,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Employees |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross | 3,000 |  |  | 3,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Employees | General and Administrative Expense [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Allocated Share-based Compensation Expense | $ 5,000,000 |  |  | $ 5,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
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 | 515 |  |  | 515 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 7,143
Amended Stock Plan 2010 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Common Stock, Capital Shares Reserved for Future Issuance |  |  |  |  |  |  |  |  |  | 400,000 | 100,000 | 100,000 | 50,000 | 50,000 | 40,000 | 40,000 | 22,858 | 22,858 | 17,143 | 17,143 | 8,572 |  |
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 | 368,000 |  |  | 368,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 8,572 |
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 | 238,820 |  |  | 238,820 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
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 |  |  |  |  |  |  |  |  | 400,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |

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