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Stock-Based Compensation and Warrants (Details Textual) - USD ($)			1 Months Ended		12 Months Ended
	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