Note 1 - The Company and Basis of Presentation (Details Textual) - USD ($)				1 Months Ended						3 Months Ended			11 Months Ended	12 Months Ended
	Nov. 26, 2019	Nov. 12, 2019	Aug. 16, 2019	Feb. 29, 2020	Jan. 31, 2020	Dec. 31, 2019		Nov. 30, 2019	Aug. 31, 2019	Mar. 31, 2020	Sep. 30, 2019	Mar. 31, 2019	Nov. 30, 2019	Dec. 31, 2019		Dec. 31, 2018
Class of Warrant or Right, Number of Securities Called by Warrants or Rights (in shares)										23,665,905
Proceeds from Warrant Exercises										$ 1,661,000
Retained Earnings (Accumulated Deficit), Ending Balance						$ (197,911,000)	[1]			(204,221,000)				$ (197,911,000)	[1]
Cash and Cash Equivalents, at Carrying Value, Ending Balance						$ 13,308,000	[1]			9,042,000		17,821,000		$ 13,308,000	[1]	$ 29,523,000
Working Capital										12,399,000
Net Cash Provided by (Used in) Operating Activities, Total										$ (5,736,000)		$ (11,558,000)
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
Series A Convertible Preferred Stock Into Common Stock [Member]
Conversion of Stock, Shares Converted (in shares)				669,022	1,183,151	3,021,237		600,000
Series B Convertible Preferred Stock Into Common Stock [Member] | Minimum [Member]
Conversion of Stock, Conversion Rate (in dollars per share)		$ 1.53
Series B Convertible Preferred Stock Into Common Stock [Member] | Maximum [Member]
Conversion of Stock, Conversion Rate (in dollars per share)		$ 1.836
Series A Preferred Stock [Member]
Convertible Preferred Stock, Shares Issued upon Conversion (in shares)								1		1			1
Preferred Stock, Shares Outstanding, Ending Balance (in shares)						1,852,173	[2]			0				1,852,173	[2]
Series A Convertible Preferred Stock [Member]
Preferred Stock, Shares Outstanding, Ending Balance (in shares)										0
Series A Warrants [Member]
Class of Warrant or Right, Number of Securities Called by Each Warrant or Right (in shares)								1					1
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)								$ 1.55		$ 1.55			$ 1.55
Warrants and Rights Outstanding, Term (Year)								1 year					1 year
Class of Warrant or Right, Number of Securities Called by Warrants or Rights (in shares)								7,419,353		6,393,113			7,419,353
Stock Issued During Period, Shares, Warrant Exercises (in shares)				1,026,240
Proceeds from Warrant Exercises				$ 1,591,000
Series B Warrants [Member]
Class of Warrant or Right, Number of Securities Called by Each Warrant or Right (in shares)								1					1
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)								$ 1.55		$ 1.55			$ 1.55
Warrants and Rights Outstanding, Term (Year)								5 years					5 years
Class of Warrant or Right, Number of Securities Called by Warrants or Rights (in shares)								7,419,353		7,373,880			7,419,353
Stock Issued During Period, Shares, Warrant Exercises (in shares)				45,473
Proceeds from Warrant Exercises				$ 70,000
Warrants Issued Upon Conversion of Term Loan with CRG [Member]
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)										$ 1.84
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								9,893,776
Class of Warrants and Rights Outstanding, Exercise Price Percentage of Conversion Rate		120.00%
Class A Units [Member] | Series A Warrants [Member]
Class of Warrant or Right, Number of Securities Called by Each Warrant or Right (in shares)								1					1
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)								$ 1.55					$ 1.55
Warrants and Rights Outstanding, Term (Year)								1 year					1 year
Class A Units [Member] | Series B Warrants [Member]
Class of Warrant or Right, Number of Securities Called by Each Warrant or Right (in shares)								1					1
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)								$ 1.55					$ 1.55
Warrants and Rights Outstanding, Term (Year)								5 years					5 years
Class B Units [Member] | Series A Warrants [Member]
Class of Warrant or Right, Number of Securities Called by Each Warrant or Right (in shares)								1					1
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)								$ 1.55					$ 1.55
Warrants and Rights Outstanding, Term (Year)								1 year					1 year
Class B Units [Member] | Series B Warrants [Member]
Class of Warrant or Right, Number of Securities Called by Each Warrant or Right (in shares)								1					1
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)								$ 1.55					$ 1.55
Warrants and Rights Outstanding, Term (Year)								5 years					5 years
Common Stock [Member] | Series A Warrants [Member]
Stock Issued During Period, Shares, Warrant Exercises (in shares)										1,026,240
Common Stock [Member] | Series B Warrants [Member]
Stock Issued During Period, Shares, Warrant Exercises (in shares)										45,473
November 2019 Offering [Member]
Proceeds from Issuance or Sale of Equity, Total								$ 11,500,000
Proceeds From Issuance of Common Stock, Net								$ 9,922,000
November 2019 Offering [Member] | Series A Preferred Stock [Member]
Stock Issued During Period, Shares, New Issues (in shares)								5,473,410
November 2019 Offering [Member] | Class A Units [Member]
Shares Issued, Price Per Share (in dollars per share)								$ 1.55					$ 1.55
Common Shares Per Unit (in shares)								1					1
November 2019 Offering [Member] | Class B Units [Member]
Shares Issued, Price Per Share (in dollars per share)								$ 1.55					$ 1.55
Series A Convertible Preferred Stock Per Unit (in shares)								1					1
November 2019 Offering [Member] | Class B Units [Member] | Series A Preferred Stock [Member]
Convertible Preferred Stock, Shares Issued upon Conversion (in shares)								1					1
November 2019 Offering [Member] | Common Stock [Member]
Stock Issued During Period, Shares, New Issues (in shares)								1,945,943					1,945,943
August 2019 ATM Facility [Member]
Proceeds From Issuance of Common Stock, Net											$ 6,322,000			$ 6,322,000
Stock Issued During Period, Shares, New Issues (in shares)											1,004,171			1,004,171
Aggregate Offering Price			$ 6,760,000						$ 6,760,000
Stock Issued During Period, Shares, New Issues (in shares)										0
November 2017 ATM Facility [Member]
Stock Issued During Period, Shares, New Issues (in shares)										0		0

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

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