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Capital Stock - Biotechnology Value Fund Financing - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions | 1 Months Ended | 12 Months Ended
--- | --- | ---
Feb. 28, 2017 | Dec. 31, 2017 | Dec. 31, 2016
Class Of Warrant Or Right [Line Items] |  |  |
Cash proceeds from issuance of common stock and convertible preferred stock | $ 24.8 |  |
Preferred stock, stated value |  | $ 0.05 | $ 0.05
Convertible Preferred Stock (as Converted) [Member] |  |  |
Class Of Warrant Or Right [Line Items] |  |  |
Sale of shares | 5,003 |  |
Preferred stock, stated value | $ 4,030 |  |
Conversion of preferred stock into registered common stock | 1,000 |  |
Preferred stock conversion price per share | $ 4.03 |  |
Total number of shares of common stock issued upon conversion | 5,003,000 | 5,000 |
Percentage of convertible preferred stock conversion blocker provision | 19.99% |  |
Convertible preferred stock voting rights description |  | Shares of Series X convertible preferred stock will generally have no voting rights, except as required by law and except that the consent of the holders of the outstanding Series X convertible preferred stock will be required to amend the terms of the Series X preferred stock and to approve certain corporate actions. |
Ownership percentage on outstanding shares upon conversion |  | 49.10% |
Preferred shares converted |  | 0 |
Fair value of common stock amount exceeded purchase price of convertible preferred stock | $ 5.6 |  |
Common Stock [Member] |  |  |
Class Of Warrant Or Right [Line Items] |  |  |
Sale of shares | 1,200,000 | 1,849,000 | 13,000
Common stock share price | $ 4.03 |  |

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