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Stock-Based Compensation and Warrants - Additional Information (Details) - USD ($) |  |  |  |  | 1 Months Ended | 12 Months Ended |  |  |  |  |  |  |  |
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Sep. 05, 2019 | Oct. 15, 2018 | Oct. 10, 2018 | Oct. 10, 2014 | Nov. 18, 2016 | Mar. 20, 2007 | Dec. 31, 2019 | Dec. 31, 2018 | Oct. 31, 2018 | Sep. 24, 2018 | Dec. 26, 2017 | Sep. 07, 2017 | Aug. 25, 2016 | May 15, 2015 | Oct. 22, 2013 | Nov. 02, 2010
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Employee Service Share-based Compensation, Nonvested Awards, Compensation Not yet Recognized, Stock Options |  |  |  |  |  |  | $ 681,000 |  |  |  |  |  |  |  |  |
Proceeds from Stock Options Exercised |  |  |  |  |  |  | 0 | $ 0 |  |  |  |  |  |  |  |
Temporary Equity, Par or Stated Value Per Share |  |  | $ 1,000 |  |  |  |  |  |  |  |  |  |  |  |  |
Class of Warrant or Right, Outstanding |  |  | 13,672,173 |  |  |  |  |  |  |  |  |  |  |  |  |
Proceeds from Issuance or Sale of Equity |  | $ 18,600,000 |  |  |  |  | 0 | 12,172,000 |  |  |  |  |  |  |  |
Warrants Not Settleable in Cash, Fair Value Disclosure |  |  |  |  |  |  |  |  |  |  | $ 9,000 |  |  |  |  |
Class of Warrant or Right, Number of Securities Called by Warrants or Rights |  |  | 13,672,173 |  |  |  |  |  |  |  |  |  |  |  |  |
Fair Value Adjustment of Warrants |  |  |  |  |  |  | 0 | $ (4,083,000) |  |  |  |  |  |  |  |
Class of Warrant or Right, Exercise Price of Warrants or Rights |  |  | $ 1.38 |  |  |  |  |  | $ 1.38 |  |  |  |  |  |  |
Share Price |  |  | $ 0.88 | $ 61.25 |  |  |  | $ 0.56 |  |  | $ 18.55 |  |  |  |  |
IPO [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Warrants Not Settleable in Cash, Fair Value Disclosure |  |  |  |  | $ 15,700,000 |  | 100,000,000 | $ 100,000,000 |  |  |  |  |  |  |  |
Stock Issued During Period, Shares, New Issues |  |  |  |  | 714,286 |  |  |  |  |  |  |  |  |  |  |
Class of Warrant or Right, Number of Securities Called by Warrants or Rights |  |  |  |  | 1,428,571 |  |  |  |  |  |  |  |  |  |  |
Fair Value Adjustment of Warrants |  |  |  |  |  |  |  | 3,700,000 |  |  |  |  |  |  |  |
Sale of Stock, Price Per Share |  |  |  |  | $ 35.00 |  |  |  |  |  |  |  |  |  |  |
IPO [Member] | Series A [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Sale of Stock, Number of Shares Issued in Transaction |  |  | 2,520,000 |  |  |  |  |  |  |  |  |  |  |  |  |
Share Price |  |  | $ 1.15 |  |  |  |  |  |  |  |  |  |  |  |  |
IPO [Member] | Series B [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Sale of Stock, Number of Shares Issued in Transaction |  |  | 15,723 |  |  |  |  |  |  |  |  |  |  |  |  |
Share Price |  |  | $ 1,000 |  |  |  |  |  |  |  |  |  |  |  |  |
Series A Warrants [Member] | IPO [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Class of Warrant or Right, Exercise Price of Warrants or Rights |  |  |  |  | 50.05 |  |  |  |  |  |  |  |  |  |  |
Series B Warrants [Member] | IPO [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Class of Warrant or Right, Exercise Price of Warrants or Rights |  |  |  |  | $ 60.20 |  |  |  |  |  |  |  |  |  |  |
Warrant [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award Non Option Equity Instruments Warrants Exercisable Number |  |  |  |  |  |  |  |  |  |  | 714 |  |  |  |  |
General and Administrative Expenses and Research and Development Expense [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Allocated Share-based Compensation Expense |  |  |  |  |  |  | $ 300,000 | $ 1,800,000 |  |  |  |  |  |  |  |
Employees And Directors [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross |  |  |  |  |  |  | 1,725,000 | 671,500 |  |  |  |  |  |  |  |
Consultant [Member] | General and Administrative Expenses and Research and Development Expense [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Allocated Share-based Compensation Expense |  |  |  |  |  |  | $ 45,000 | $ 297,000 |  |  |  |  |  |  |  |
Employees | General and Administrative Expenses and Research and Development Expense [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Allocated Share-based Compensation Expense |  |  |  |  |  |  | $ 500,000 | 300,000 |  |  |  |  |  |  |  |
2007 Stock Plan [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number |  |  |  |  |  | 71,429 | 7,052 |  |  |  |  |  |  |  |  |
2007 Stock Plan [Member] | Maximum [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross |  |  |  |  |  | 7,143 |  |  |  |  |  |  |  |  |  |
2010 Stock Plan [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number |  |  |  |  |  |  | 2,494,960 |  |  |  |  |  |  |  |  | 85,714
2010 Stock Plan [Member] | Maximum [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross | 4,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Common Stock, Capital Shares Reserved for Future Issuance |  |  |  |  |  |  |  |  |  | 1,000,000 |  | 500,000 | 400,000 | 228,572 | 171,429 |
2010 Stock Plan [Member] | Minimum [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross | 1,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Common Stock, Capital Shares Reserved for Future Issuance |  |  |  |  |  |  |  |  |  | 500,000 |  | 400,000 | 228,572 | 171,429 | 85,714 |
Series A Warrants [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Warrants, Exercisable Number |  |  |  | 200,852 |  |  |  |  |  |  |  |  |  |  |  |
Warrants Not Settleable in Cash, Fair Value Disclosure |  |  |  |  |  |  | $ 0 | 0 |  |  |  |  |  |  |  |
Proceeds from Issuance of Common Stock |  |  |  | $ 19,100,000 |  |  |  |  |  |  |  |  |  |  |  |
Sale of Stock, Number of Shares Issued in Transaction |  |  |  | 14,059,616 |  |  |  |  |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award Warrants Vested and Expected To Vest Outstanding Number |  |  |  | 61.25 |  |  |  |  |  |  |  |  |  |  |  |
Fair Value Adjustment of Warrants |  |  |  | $ 7,400,000 |  |  |  | $ 416,000,000,000 |  |  |  |  |  |  |  |
Sale of Stock, Price Per Share |  |  |  | $ 1.47 |  |  |  |  |  |  |  |  |  |  |  |
Issue of warrants to purchase common stock |  |  |  | 0.50 |  |  |  |  |  |  |  |  |  |  |  |
Series B Preferred Stock [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Stock Issued During Period, Shares, New Issues |  |  |  |  |  |  |  | 15,723 |  |  |  |  |  |  |  |
Preferred Stock Conversion Price Per Share |  | $ 1.15 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Stock Issued During Period, Value, Issued for Services |  | $ 1,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Preferred Stock, Par or Stated Value Per Share |  | $ 1,000 |  |  |  |  | $ 1,000 | $ 1,000 |  |  |  |  |  |  |  |
Conversion of Stock, Shares Converted |  | 13,672,173 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Class of Warrant or Right, Exercise Price of Warrants or Rights |  |  |  |  |  |  |  |  | $ 1.38 |  |  |  |  |  |  |
Series B Preferred Stock [Member] | Warrant [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Class of Warrant or Right, Number of Securities Called by Warrants or Rights |  | 13,672,173 |  |  |  |  |  |  |  |  |  |  |  |  |  |

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- Definition Gross number of share options (or share units) granted during the period. + References No definition available. + Details
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