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Stockholders' Equity - Additional Information (Detail) - USD ($) |  |  | 9 Months Ended | 12 Months Ended |
--- | --- | --- | --- | --- | ---
Sep. 21, 2021 | Dec. 23, 2020 | Sep. 30, 2021 | Dec. 31, 2020 | Mar. 31, 2021
Series X1 Non-voting Convertible Preferred Stock [Member] |  |  |  |  |
Class Of Stock [Line Items] |  |  |  |  |
Preferred shares outstanding |  |  | 108,070 | 108,070 |
Series X1 Preferred Stock [Member] |  |  |  |  |
Class Of Stock [Line Items] |  |  |  |  |
Warrants available for exercise |  |  | 50,207.419 |  |
Shares of common stock issued upon conversion of each share of preferred stock |  |  | 55.5556 |  |
Series X Preferred Stock [Member] |  |  |  |  |
Class Of Stock [Line Items] |  |  |  |  |
Preferred shares outstanding |  |  | 6,204 | 0 |
Common Stock [Member] |  |  |  |  |
Class Of Stock [Line Items] |  |  |  |  |
Common stock number of shares issued |  | 1,004,111 |  |  |
Warrants available for exercise |  |  | 1,145,631 |  |
Warrants issued | 298,692 |  |  |  |
Common Stock [Member] | Series X1 Non-voting Convertible Preferred Stock [Member] |  |  |  |  |
Class Of Stock [Line Items] |  |  |  |  |
Warrants exercisable for exchange | 5,376.456 |  |  |  |
Warrant Exchange Agreement and Exchange Agreements [Member] | Series X Preferred Stock [Member] |  |  |  |  |
Class Of Stock [Line Items] |  |  |  |  |
Preferred shares outstanding |  |  |  | 6,203.98 |
Warrant Exchange Agreement and Exchange Agreements [Member] | Common Stock [Member] | Series X Preferred Stock [Member] |  |  |  |  |
Class Of Stock [Line Items] |  |  |  |  |
Shares of common stock issued upon conversion of each share of preferred stock |  |  |  | 344,663 |
Exchange Agreement [Member] |  |  |  |  |
Class Of Stock [Line Items] |  |  |  |  |
Warrants available for exercise |  |  | 509,117 |  |
Jeffries LLC [Member] | Equity Distribution Agreement [Member] |  |  |  |  |
Class Of Stock [Line Items] |  |  |  |  |
Equity distribution agreement maximum value of common shares issuable |  |  |  |  | $ 75,000,000.0
Common stock number of shares issued |  |  | 0 |  |
BVF Exchanging Stockholders, Series X Exchanging Stockholders [Member] | Series X Exchange Agreement [Member] | Series X Preferred Stock [Member] |  |  |  |  |
Class Of Stock [Line Items] |  |  |  |  |
Conversion of stock, shares issued |  |  |  | 6,203.98 |
BVF Exchanging Stockholders, Series X Exchanging Stockholders [Member] | Series X Exchange Agreement [Member] | Common Stock [Member] |  |  |  |  |
Class Of Stock [Line Items] |  |  |  |  |
Conversion of stock, shares converted |  |  |  | 344,666 |
BVF Exchanging Stockholders | Warrant Exchange Agreement and Exchange Agreements [Member] | Common Stock [Member] |  |  |  |  |
Class Of Stock [Line Items] |  |  |  |  |
Warrants to issue shares of common stock |  |  |  | 509,117 |

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