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Basis of Presentation and Summary of Significant Accounting Policies - Financial Instruments (Details) - USD ($) $ / shares in Units, $ in Thousands |  | 1 Months Ended | 3 Months Ended | 12 Months Ended
--- | --- | --- | --- | ---
Dec. 16, 2021 | Dec. 31, 2021 | Jun. 30, 2021 | Jan. 31, 2020 | Mar. 31, 2022 | Mar. 31, 2021 | Dec. 31, 2021
Class of Stock [Line Items] |  |  |  |  |  |  |
Amount paid for clearing fees |  |  | $ 19 |  |  |  |
Warrants issued (in shares) |  |  |  |  | 229,414 | 310,860 |
Proceeds from the exercise of warrants |  |  |  |  | $ 0 |  |
December 2021 Private Placement |  |  |  |  |  |  |
Class of Stock [Line Items] |  |  |  |  |  |  |
Sale of common stock (in shares) |  | 1,193,185 |  |  |  |  |
Sale of common stock (USD per share) |  | $ 3.52 |  |  |  |  | $ 3.52
Securities called by warrants (in shares) |  |  |  |  | 1,278,413 |  |
Exercise price of common stock (USD per share) |  |  |  |  | $ 3.52 |  |
Amount paid for placement agent commissions |  | $ 360 |  |  |  |  |
Amount paid related to expenses for registered direct offering and concurrent private placement |  | 42 |  |  |  |  |
Amount paid for clearing fees |  | 97 |  |  |  |  |
Offering costs paid on the issuance of common stock and warrants |  | 499 |  |  |  |  |
Proceeds from sale of common stock and warrants |  | $ 4,000 |  |  |  |  |
Estimated proceeds from issuance of warrants |  |  |  |  | $ 4,500 |  |
December 2021 Private Placement | Pre-Funded Warrants |  |  |  |  |  |  |
Class of Stock [Line Items] |  |  |  |  |  |  |
Securities called by warrants (in shares) |  | 85,228 |  |  |  |  | 85,228
Exercise price of common stock (USD per share) |  | $ 0.0001 |  |  |  |  | $ 0.0001
Warrants issued (in shares) | 85,228 |  |  |  |  |  |
December 2021 Private Placement | Warrants |  |  |  |  |  |  |
Class of Stock [Line Items] |  |  |  |  |  |  |
Securities called by warrants (in shares) |  | 1,278,413 |  |  |  |  | 1,278,413
Exercise price of common stock (USD per share) |  | $ 3.52 |  |  |  |  | $ 3.52
Investor Warrants |  |  |  |  |  |  |
Class of Stock [Line Items] |  |  |  |  |  |  |
Sale of common stock (in shares) |  |  | 990,100 |  |  |  |
Sale of common stock (USD per share) |  |  | $ 5.05 |  |  |  |
Exercise price of common stock (USD per share) |  |  |  | $ 3.37 |  |  |
Amount paid for placement agent commissions |  |  | $ 400 |  |  |  |
Amount paid related to expenses for registered direct offering and concurrent private placement |  |  | 51 |  |  |  |
Offering costs paid on the issuance of common stock and warrants |  |  |  |  |  |  | $ 470
Proceeds from sale of common stock and warrants |  |  | $ 4,500 |  |  |  |
Warrants issued (in shares) |  |  |  |  | 187,734 | 269,180 |
January 2020 Equity Offering |  |  |  |  |  |  |
Class of Stock [Line Items] |  |  |  |  |  |  |
Exercise price of common stock (USD per share) |  |  |  |  | $ 3.67 | $ 3.59 |
Amount paid for placement agent commissions |  |  |  | $ 193 |  |  |
Amount paid related to expenses for registered direct offering and concurrent private placement |  |  |  | 50 |  |  |
Amount paid for clearing fees |  |  |  | 231 |  |  |
Offering costs paid on the issuance of common stock and warrants |  |  |  |  |  |  | $ 510
Proceeds from sale of common stock and warrants |  |  |  | $ 2,300 |  |  |
Warrants issued (in shares) |  |  |  |  | 229,414 | 310,860 |
Estimated proceeds from issuance of warrants |  |  |  |  | $ 800 |  |
Proceeds from the exercise of warrants |  |  |  |  |  | $ 527 |
Warrants exercised (in shares) |  |  |  |  | 0 | (156,446) |
January 2020 Institutional Investor |  |  |  |  |  |  |
Class of Stock [Line Items] |  |  |  |  |  |  |
Sale of common stock (in shares) |  |  |  | 688,360 |  |  |
Sale of common stock (USD per share) |  |  |  | $ 3.3700 |  |  |
Securities called by warrants (in shares) |  |  |  | 688,360 |  |  |
Purchase price (USD per share) |  |  |  | $ 0.625 |  |  |
January 2020 Equity Offering, Private Placement |  |  |  |  |  |  |
Class of Stock [Line Items] |  |  |  |  |  |  |
Securities called by warrants (in shares) |  |  |  | 48,185 |  |  |
Exercise price of common stock (USD per share) |  |  |  | $ 4.9940 |  |  |
Warrants issued (in shares) |  |  |  |  | 41,680 | 41,680 |

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