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Common Stock Warrants - Summary of Outstanding Warrants to Purchase Shares of Common Stock (Detail) - USD ($) $ / shares in Units, $ in Thousands | Sep. 30, 2021 | Mar. 23, 2021 | Dec. 31, 2020 | Nov. 29, 2019 | Apr. 16, 2019
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Class of Warrant or Right [Line Items] |  |  |  |  |
Number of Shares of Common Stock Issuable (in shares) | 11,249,128 |  | 13,354,403 |  |
Class Of Warrant Or Right. Aggregate Proceeds From Warrants Issued |  | $ 435 |  | $ 21,000 |
Class of Warrant or Right, Additional Exercise Price of Warrants or Rights |  | $ 0.01 |  | $ 0.001 |
Funded |  |  |  |  |
Class of Warrant or Right [Line Items] |  |  |  |  |
Exercise Price (usd per share) |  | 8.69 |  |  |
Pre Funded Warrant |  |  |  |  |
Class of Warrant or Right [Line Items] |  |  |  |  |
Exercise Price (usd per share) |  |  |  | 11.999 | $ 10.999
Class B Warrants |  |  |  |  |
Class of Warrant or Right [Line Items] |  |  |  |  |
Exercise Price (usd per share) |  | $ 8.70 |  | 15.00 |
Class A Warrant |  |  |  |  |
Class of Warrant or Right [Line Items] |  |  |  |  |
Exercise Price (usd per share) |  |  |  |  | $ 13.20
Issuance On October 25, 2016 |  |  |  |  |
Class of Warrant or Right [Line Items] |  |  |  |  |
Exercise Price (usd per share) | $ 19.78 |  |  |  |
Issuance On October 25, 2016 | Legacy Warrants |  |  |  |  |
Class of Warrant or Right [Line Items] |  |  |  |  |
Number of Shares of Common Stock Issuable (in shares) | 5,155 |  |  |  |
Issuance On December 28, 2017 One |  |  |  |  |
Class of Warrant or Right [Line Items] |  |  |  |  |
Exercise Price (usd per share) | $ 19.78 |  |  |  |
Issuance On December 28, 2017 One | Legacy Warrants |  |  |  |  |
Class of Warrant or Right [Line Items] |  |  |  |  |
Number of Shares of Common Stock Issuable (in shares) | 115,916 |  |  |  |
Issuance On September 12, 2018 One |  |  |  |  |
Class of Warrant or Right [Line Items] |  |  |  |  |
Exercise Price (usd per share) | $ 19.78 |  |  |  |
Issuance On September 12, 2018 One | Legacy Warrants |  |  |  |  |
Class of Warrant or Right [Line Items] |  |  |  |  |
Number of Shares of Common Stock Issuable (in shares) | 20,220 |  |  |  |
Issuance On October 19, 2018 |  |  |  |  |
Class of Warrant or Right [Line Items] |  |  |  |  |
Exercise Price (usd per share) | $ 19.78 |  |  |  |
Issuance On October 19, 2018 | Legacy Warrants |  |  |  |  |
Class of Warrant or Right [Line Items] |  |  |  |  |
Number of Shares of Common Stock Issuable (in shares) | 20,016 |  |  |  |
Issuance On March 13, 2019 |  |  |  |  |
Class of Warrant or Right [Line Items] |  |  |  |  |
Exercise Price (usd per share) | $ 19.78 |  |  |  |
Issuance On March 13, 2019 | Legacy Warrants |  |  |  |  |
Class of Warrant or Right [Line Items] |  |  |  |  |
Number of Shares of Common Stock Issuable (in shares) | 5,000 |  |  |  |
Issuance On April 16, 2019 |  |  |  |  |
Class of Warrant or Right [Line Items] |  |  |  |  |
Exercise Price (usd per share) | $ 13.20 |  |  |  |
Issuance On April 16, 2019 | Class A Warrant |  |  |  |  |
Class of Warrant or Right [Line Items] |  |  |  |  |
Number of Shares of Common Stock Issuable (in shares) | 3,866,154 |  |  |  |
Issuance On November 29, 2019 |  |  |  |  |
Class of Warrant or Right [Line Items] |  |  |  |  |
Exercise Price (usd per share) | $ 8.70 |  |  |  |
Issuance On November 29, 2019 | Class B Warrants |  |  |  |  |
Class of Warrant or Right [Line Items] |  |  |  |  |
Number of Shares of Common Stock Issuable (in shares) | 5,416,667 |  |  |  |
Issuance On November 29, 2019 One |  |  |  |  |
Class of Warrant or Right [Line Items] |  |  |  |  |
Exercise Price (usd per share) | $ 12.00 |  |  |  |
Issuance On November 29, 2019 One | Pre Funded Warrant |  |  |  |  |
Class of Warrant or Right [Line Items] |  |  |  |  |
Number of Shares of Common Stock Issuable (in shares) | 1,750,000 |  |  |  |
Issuance On March 23, 2021 |  |  |  |  |
Class of Warrant or Right [Line Items] |  |  |  |  |
Exercise Price (usd per share) | $ 8.70 |  |  |  |
Issuance On March 23, 2021 | Pre Funded Warrant |  |  |  |  |
Class of Warrant or Right [Line Items] |  |  |  |  |
Number of Shares of Common Stock Issuable (in shares) | 50,000 |  |  |  |
Pre Funded Warrant |  |  |  |  |
Class of Warrant or Right [Line Items] |  |  |  |  |
Exercise Price (usd per share) |  |  |  | $ 11.999 |

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