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Stock-Based Compensation and Warrants (Details Textual) - USD ($) |  |  | 1 Months Ended | 12 Months Ended |  |  |  |  |  |  |  |  |
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Oct. 10, 2018 | Oct. 10, 2014 | Nov. 18, 2016 | Mar. 20, 2007 | Dec. 31, 2018 | Dec. 31, 2017 | Oct. 31, 2018 | Oct. 15, 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 |  |  |  |  | $ 824,000 |  |  |  |  |  |  |  |  |  |
Sale of Stock, Number of Shares Issued in Transaction |  |  |  |  | 3,500,000 |  |  |  |  |  |  |  |  |  |
Change in fair value of warrant liabilities |  |  |  |  | $ (4,083,000) | $ (10,738,000) |  |  |  |  |  |  |  |  |
Class of Warrant or Right, Number of Securities Called by Warrants or Rights | 13,672,173 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Class of Warrant or Right, Exercise Price of Warrants or Rights | $ 1.38 |  |  |  |  |  | $ 1.38 |  |  |  |  |  |  |  |
Warrants Not Settleable in Cash, Fair Value Disclosure |  |  |  |  |  |  |  |  |  | $ 9,000 |  |  |  |  |
Proceeds from Stock Options Exercised |  |  |  |  | $ 0 | $ 166,000 |  |  |  |  |  |  |  |  |
Common Stock, Par or Stated Value Per Share | 0.001 |  |  |  | $ 0.001 | $ 0.001 |  |  |  |  |  |  |  |  |
Share Price |  | $ 61.25 |  |  | $ 0.56 | $ 17.85 |  |  |  |  |  |  |  |  |
Temporary Equity, Par or Stated Value Per Share | $ 1,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Class of Warrant or Right, Outstanding | 13,672,173 |  |  |  |  |  |  |  |  |  |  |  |  |  |
IPO [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Sale of Stock, Price Per Share |  |  | $ 35.00 |  |  |  |  |  |  |  |  |  |  |  |
Change in fair value of warrant liabilities |  |  |  |  | $ 3,700,000 | $ 9,000,000 |  |  |  |  |  |  |  |  |
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 |  |  |  |  |  |  |  |  |  |  |  |
Warrants Not Settleable in Cash, Fair Value Disclosure |  |  | $ 15,700,000 |  | 100,000,000 | $ 3,700,000 |  |  |  |  |  |  |  |  |
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 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Over-Allotment Option [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Stock Issued During Period, Shares, New Issues | 2,428,825 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Class of Warrant or Right, Number of Securities Called by Warrants or Rights | 2,428,825 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Issue of warrants to purchase common stock | 1,807,826 |  |  |  |  |  |  |  |  |  |  |  |  |  |
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] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Change in fair value of warrant liabilities |  |  |  |  | $ 416,000 |  |  |  |  |  |  |  |  |  |
Class of Warrant or Right, Number of Securities Called by Warrants or Rights |  |  |  |  |  |  |  | 13,672,173 |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award Non Option Equity Instruments Warrants Exercisable Number |  |  |  |  |  |  |  |  |  | 714 |  |  |  |  |
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 |  |  |  |  | 671,500 | 90,262 |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Fair Value |  |  |  |  | $ 300,000 | $ 1,800,000 |  |  |  |  |  |  |  |  |
Employee [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 |  |  |  |  | 1,800,000 | 3,000,000 |  |  |  |  |  |  |  |  |
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 |  |  |  |  | $ 297,000 | 434,000 |  |  |  |  |  |  |  |  |
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 | 18,645 |  |  |  |  |  |  |  |  |  |
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 |  |  |  |  | 920,337 |  |  |  |  |  |  |  |  |  | 85,714
2010 Stock Plan [Member] | Maximum [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
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] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Common Stock, Capital Shares Reserved for Future Issuance |  |  |  |  |  |  |  |  | 500,000 |  | 400,000 | 228,572 | 171,429 | 85,714 |
Stock 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 |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Warrants, Vested and Expected to Vest Outstanding, Number |  | 61.25 |  |  |  |  |  |  |  |  |  |  |  |  |
Sale of Stock, Number of Shares Issued in Transaction |  | 14,059,616 |  |  |  |  |  |  |  |  |  |  |  |  |
Sale of Stock, Price Per Share |  | $ 1.47 |  |  |  |  |  |  |  |  |  |  |  |  |
Proceeds from Issuance of Common Stock |  | $ 19,100,000 |  |  |  |  |  |  |  |  |  |  |  |  |
Change in fair value of warrant liabilities |  | $ 7,400,000 |  |  |  | 1,700,000 |  |  |  |  |  |  |  |  |
Warrants Not Settleable in Cash, Fair Value Disclosure |  |  |  |  | $ 0 | $ 416,000 |  |  |  |  |  |  |  |  |
Issue of warrants to purchase common stock |  | 0.50 |  |  |  |  |  |  |  |  |  |  |  |  |

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- Definition The value as of the balance sheet date at which grantees can acquire the shares reserved for issuance on vested portions of options outstanding and currently exercisable under the share warrants plan. + References No definition available. + Details
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- Definition Fair value of stock (or other type of equity) granted during the period as a result of any equity-based compensation plan other than an employee stock ownership plan (ESOP). + References No definition available. + Details
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- Definition The number of exercisable share warrants that may be converted as of the balance sheet date. + References No definition available. + Details
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- Definition As of the balance sheet date, the number of warrants into which fully vested and expected to vest stock options outstanding can be converted under the option plan. + References No definition available. + Details
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- Definition Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5047-113901 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB Topic 14.F) -URI http://asc.fasb.org/extlink&oid=115993241&loc=d3e301413-122809 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (h)(1)(i) -URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901 + Details
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- Definition Number of securities into which the class of warrant or right may be converted. For example, but not limited to, 500,000 warrants may be converted into 1,000,000 shares. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.4-08.(i)(2)) -URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690 + Details
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- Definition Aggregate number of common shares reserved for future issuance. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.29) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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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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- Definition Fair value portion of warrants not settleable in cash classified as equity. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=99377789&loc=d3e19207-110258 + Details
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