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Stockholders' Equity - Common stock (Details) - USD ($) |  |  |  |  |  | 9 Months Ended | 12 Months Ended |
--- | --- | --- | --- | --- | --- | --- | --- | ---
Feb. 24, 2022 | Jan. 14, 2022 | Jan. 01, 2022 | Sep. 30, 2020 | Jun. 16, 2020 | Sep. 30, 2020 | Dec. 31, 2021 | Dec. 31, 2020 | Oct. 23, 2020
Class of Stock [Line Items] |  |  |  |  |  |  |  |  |
Sale of common stock, net |  |  |  |  |  |  | $ 18,581,000 | $ 3,882,000 |
Proceeds from sale of common stock |  |  |  |  |  |  | 18,675,000 | 4,007,000 |
Common Stock [Member] |  |  |  |  |  |  |  |  |
Class of Stock [Line Items] |  |  |  |  |  |  |  |  |
Sale of common stock, net |  |  |  |  |  |  | $ 8,000 | $ 2,000 |
Common stock issued (in shares) |  |  |  |  |  |  | 7,864,379 | 2,150,113 |
2020 Repurchase Agreement [Member] | Lincoln Park Capital Fund, LLC [Member] | Common Stock [Member] |  |  |  |  |  |  |  |  |
Class of Stock [Line Items] |  |  |  |  |  |  |  |  |
Sale of common stock, net |  |  |  |  |  | $ 25,000,000.0 |  |  |
Common stock issued (in shares) |  |  |  |  |  |  | 5,685,186 | 353,113 |
Period exercisable from the date of issuance |  |  |  |  |  | 36 months |  |  |
Closing price per share |  |  |  |  | $ 1.05 |  |  |  |
Proceeds from sale of common stock |  |  |  |  |  |  | $ 12,500,000 | $ 700,000 |
2020 Repurchase Agreement [Member] | Lincoln Park Capital Fund, LLC [Member] | Common Stock [Member] | Subsequent Event [Member] |  |  |  |  |  |  |  |  |
Class of Stock [Line Items] |  |  |  |  |  |  |  |  |
Common stock issued (in shares) |  |  | 5,665,000 |  |  |  |  |  |
Proceeds from sale of common stock |  |  | $ 7,000,000.0 |  |  |  |  |  |
Remaining common stock issued and sold (in shares) |  |  | 0 |  |  |  |  |  |
2020 Repurchase Agreement [Member] | Lincoln Park Capital Fund, LLC [Member] | Common Stock [Member] | Commitment Fee [Member] |  |  |  |  |  |  |  |  |
Class of Stock [Line Items] |  |  |  |  |  |  |  |  |
Common stock issued (in shares) |  |  |  |  |  |  |  | 180,701 |
2020 Repurchase Agreement [Member] | Lincoln Park Capital Fund, LLC [Member] | Common Stock [Member] | Minimum [Member] |  |  |  |  |  |  |  |  |
Class of Stock [Line Items] |  |  |  |  |  |  |  |  |
Percentage issuance of common stock |  |  |  |  | 19.99% |  |  |  |
2020 Repurchase Agreement [Member] | Lincoln Park Capital Fund, LLC [Member] | Common Stock [Member] | Minimum [Member] | Single Regular Purchase [Member] |  |  |  |  |  |  |  |  |
Class of Stock [Line Items] |  |  |  |  |  |  |  |  |
Sale of common stock, net |  |  |  | $ 500,000 |  |  |  |  |
Common stock issued (in shares) |  |  |  | 50,000 |  |  |  |  |
2020 Repurchase Agreement [Member] | Lincoln Park Capital Fund, LLC [Member] | Common Stock [Member] | Maximum [Member] |  |  |  |  |  |  |  |  |
Class of Stock [Line Items] |  |  |  |  |  |  |  |  |
Common stock issued (in shares) |  |  |  |  | 23,800,000 |  |  |  |
2020 Repurchase Agreement [Member] | Lincoln Park Capital Fund, LLC [Member] | Common Stock [Member] | Maximum [Member] | Single Regular Purchase [Member] |  |  |  |  |  |  |  |  |
Class of Stock [Line Items] |  |  |  |  |  |  |  |  |
Common stock issued (in shares) |  |  |  | 100,000 |  |  |  |  |
Closing price per share |  |  |  | $ 0.25 |  | $ 0.25 |  |  |
Sales Agreement [Member] | Canaccord Genuity LLC [Member] | Common Stock [Member] | At The Market Offering Program [Member] |  |  |  |  |  |  |  |  |
Class of Stock [Line Items] |  |  |  |  |  |  |  |  |
Remaining availability under financing facility |  |  |  |  |  |  |  |  | $ 0
Sales Agreement [Member] | Canaccord Genuity LLC [Member] | Common Stock [Member] | Subsequent Event [Member] | At The Market Offering Program [Member] |  |  |  |  |  |  |  |  |
Class of Stock [Line Items] |  |  |  |  |  |  |  |  |
Remaining availability under financing facility |  | $ 0 |  |  |  |  |  |  |
Sales Agreement [Member] | Canaccord Genuity LLC [Member] | Common Stock [Member] | Maximum [Member] | Subsequent Event [Member] | At The Market Offering Program [Member] |  |  |  |  |  |  |  |  |
Class of Stock [Line Items] |  |  |  |  |  |  |  |  |
Proceeds from sale of common stock |  | $ 5,000,000 |  |  |  |  |  |  |
2022 Distribution Agreement [Member] | Common Stock [Member] | Subsequent Event [Member] |  |  |  |  |  |  |  |  |
Class of Stock [Line Items] |  |  |  |  |  |  |  |  |
Common stock issued (in shares) | 1,000,000 |  |  |  |  |  |  |  |
Proceeds from sale of common stock | $ 900,000 |  |  |  |  |  |  |  |
2022 Distribution Agreement [Member] | Canaccord Genuity LLC [Member] | Common Stock [Member] | Subsequent Event [Member] |  |  |  |  |  |  |  |  |
Class of Stock [Line Items] |  |  |  |  |  |  |  |  |
Common stock issued (in shares) |  |  | 1,000,000 |  |  |  |  |  |
Proceeds from sale of common stock |  |  | $ 900,000 |  |  |  |  |  |
2020 Distribution Agreement [Member] | Canaccord Genuity LLC [Member] | Common Stock [Member] |  |  |  |  |  |  |  |  |
Class of Stock [Line Items] |  |  |  |  |  |  |  |  |
Common stock issued (in shares) |  |  |  |  |  |  | 2,179,193 | 1,616,331 |
Proceeds from sale of common stock |  |  |  |  |  |  | $ 6,300,000 | $ 3,200,000 |
Remaining availability under financing facility |  |  |  |  |  |  | $ 0 |  |

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