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Liquidity and Going Concern - Additional Information (Details) - USD ($) | 3 Months Ended |  |  |  |
--- | --- | --- | --- | --- | ---
Jun. 30, 2020 | Mar. 31, 2020 | Mar. 31, 2019 | Apr. 30, 2020 | Dec. 31, 2019 | Jun. 30, 2019 | Dec. 31, 2018
Liquidity [Line Items] |  |  |  |  |  |  |
Net loss |  | $ 1,087,000 | $ 3,150,000 |  |  |  |
Accumulated deficit |  | (426,357,000) |  |  | $ (425,270,000) |  |
Net cash used in operating activities |  | $ (1,502,000) | (3,270,000) |  |  |  |
Substantial doubt about going concern, description |  | These factors raise substantial doubt about the Company?s ability to continue as a going concern. |  |  |  |  |
Stockholders' equity (deficit) |  | $ 85,000 | 3,857,000 |  | 1,160,000 |  | $ 5,225,000
Excercise price |  | $ 2.25 |  |  |  |  |
Warrant liability |  | $ 5,262,000 |  |  | $ 6,929,000 |  |
Change in fair value of warrants |  | (1,667,000) | $ (210,000) |  |  |  |
Scenario Forecast [Member] |  |  |  |  |  |  |
Liquidity [Line Items] |  |  |  |  |  |  |
Change in fair value of warrants | $ 700,000 |  |  |  |  |  |
Subsequent Event [Member] |  |  |  |  |  |  |
Liquidity [Line Items] |  |  |  |  |  |  |
Warrant liability |  |  |  | $ 4,200,000 |  |  |
Nasdaq Stock Market LLC [Member] |  |  |  |  |  |  |
Liquidity [Line Items] |  |  |  |  |  |  |
Stockholders' equity (deficit) |  | (85,000) |  |  |  | $ 6,300,000 |
Minimum stockholders equity requirement |  | $ 2,500,000 |  |  |  |  |

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