Note 6 - Note Payable (Details Textual) - USD ($)					3 Months Ended		9 Months Ended		12 Months Ended
	Nov. 26, 2019	Nov. 12, 2019	Dec. 29, 2017	May 22, 2017	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Class of Warrant or Right, Number of Securities Called by Warrants or Rights (in shares)					17,710,876		17,710,876
Notes Payable, Noncurrent, Total					$ 4,377,000		$ 4,377,000		$ 3,983,000	[1]
Gains (Losses) on Restructuring of Debt									(6,705,000)
Series B Preferred Stock [Member]
Conversion of Stock, Conversion Rate (in dollars per share)					$ 1.53		$ 1.53
Preferred Stock, Fair Value, Per Share (in dollars per share)	$ 1,023.23
Convertible Preferred Stock, Fair Value	$ 32,027,000
Minimum [Member] | Series B Convertible Preferred Stock Into Common Stock [Member]
Conversion of Stock, Conversion Rate (in dollars per share)		$ 1.53
Maximum [Member] | Series B Convertible Preferred Stock Into Common Stock [Member]
Conversion of Stock, Conversion Rate (in dollars per share)		$ 1.836
Conversion of Term Loan with CRG Into Stock and Warrants [Member]
Debt Conversion, Original Debt, Amount		$ 28,981,000
Debt Conversion, Converted Instrument, Amount		$ 31,300,000
Conversion of Term Loan with CRG Into Series B Convertible Preferred Stock [Member]
Debt Conversion, Converted Instrument, Shares Issued (in shares)	31,300	31,300
May 2017 Issuance Related to 2017 Loan Agreement [Member]
Warrants and Rights Outstanding, Term (Year)				10 years
Class of Warrant or Right, Number of Securities Called by Warrants or Rights (in shares)				2,220
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)				$ 950
Warrants and Rights Outstanding				$ 940,000
Warrants Issued Upon Conversion of Term Loan with CRG [Member]
Warrants and Rights Outstanding, Term (Year)		5 years
Class of Warrant or Right, Number of Securities Called by Warrants or Rights (in shares)	9,893,776	9,893,776
Class of Warrants and Rights Outstanding, Exercise Price Percentage of Conversion Rate		120.00%
Warrants and Rights Outstanding		$ 3,502,000			$ 3,502,000		$ 3,502,000
The 2017 Loan Agreement [Member]
Notes Payable, Noncurrent, Total					4,377,000		4,377,000
The 2017 Loan Agreement [Member] | CRG LP [Member]
Debt Instrument, Face Amount				20,000,000
Debt Agreement, Covenant, Additional Funding				10,000,000
Debt Agreement, Maximum Borrowing Capacity				$ 30,000,000
Proceeds from Lines of Credit, Total			$ 10,000,000
Debt Instrument, Term (Year)				6 years
Debt instrument, Interest Only Payment, Period (Year)				4 years
Debt Instrument, Interest Rate, Stated Percentage				12.50%
Debt Instrument, Interest Rate, Stated Percentage Deferred During Interest-only Period				4.00%
Paid-in-Kind Interest					136,000	$ 331,000	392,000	$ 973,000
Debt Instrument, Prepayment Fee, Percentage				5.00%
Debt Instrument, Back-end Facility Fee Percentage of Principal		25.00%		5.00%
Notes Payable, Noncurrent, Total					$ 4,377,000		$ 4,377,000		$ 3,983,000

[1] The condensed consolidated balance sheet as of December 31, 2019 has been derived from the audited consolidated financial statements as of that date.