Note 10 - Common Stock (Details Textual)		1 Months Ended								3 Months Ended			11 Months Ended	12 Months Ended
	Aug. 16, 2019 USD ($)	Mar. 31, 2020 USD ($) $ / shares shares	Feb. 29, 2020 USD ($) shares	Jan. 31, 2020 shares	Dec. 31, 2019 USD ($) shares	Nov. 30, 2019 USD ($) $ / shares shares	Oct. 31, 2019 USD ($)	Aug. 31, 2019 USD ($)	Mar. 31, 2019 USD ($)	Mar. 31, 2020 USD ($) $ / shares shares	Sep. 30, 2019 USD ($) shares	Mar. 31, 2019 USD ($) shares	Nov. 30, 2019 USD ($) $ / shares shares	Dec. 31, 2019 USD ($) shares	Nov. 26, 2019 USD ($) shares	Nov. 12, 2019 USD ($) $ / shares shares	May 22, 2017 USD ($) yr $ / shares shares
Class of Warrant or Right, Number of Securities Called by Warrants or Rights (in shares)		23,665,905								23,665,905
Proceeds from Warrant Exercises | $										$ 1,661,000
Stock Issued During Period, Value, Restricted Stock Award, Gross | $												25,000
Amortization of Debt Discount (Premium) | $										1,000		$ 83,000
Debt Instrument, Unamortized Discount, Total | $		$ 11,000								$ 11,000
Class of Warrants or Rights, Exercises in Period (in shares)										0		0
Class of Warrant or Right Number of Securities Called by Warrants or Rights Cancelled In Period (in shares)										0		0
Share-based Payment Arrangement, Expense | $										$ 710,000		$ 496,000
Class of Warrant or Right, Issued During Period (in shares)										0		0
The 2017 Loan Agreement [Member]
Debt Issuance Costs, Net, Total | $		790,000								$ 790,000
Restricted Stock [Member]
Proceeds From Issuance of Common Stock, Net | $		28,313			$ 30,675		$ 7,740		$ 274
Stock Issued During Period, Value, Restricted Stock Award, Gross | $		$ 24,000			$ 25,000		$ 25,000		$ 25,000
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) | $ / shares																$ 1.53
Series B Convertible Preferred Stock Into Common Stock [Member] | Maximum [Member]
Conversion of Stock, Conversion Rate (in dollars per share) | $ / shares																$ 1.836
Series A Preferred Stock [Member]
Convertible Preferred Stock, Shares Issued upon Conversion (in shares)		1				1				1			1
Series B Preferred Stock [Member]
Conversion of Stock, Conversion Rate (in dollars per share) | $ / shares		$ 1.53								$ 1.53
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) | $ / shares		$ 1.55				$ 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)		6,393,113				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
Warrants and Rights Outstanding | $						$ 1,210,000							$ 1,210,000
Series A Warrants [Member] | Measurement Input, Expected Dividend Rate [Member]
Warrants and Rights Outstanding, Measurement Input						0							0
Series A Warrants [Member] | Measurement Input, Price Volatility [Member]
Warrants and Rights Outstanding, Measurement Input						91.1							91.1
Series A Warrants [Member] | Measurement Input, Risk Free Interest Rate [Member]
Warrants and Rights Outstanding, Measurement Input						1.59							1.59
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) | $ / shares		$ 1.55				$ 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)		7,373,880				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 and Rights Outstanding | $						$ 2,871,000							$ 2,871,000
Series B Warrants [Member] | Measurement Input, Expected Dividend Rate [Member]
Warrants and Rights Outstanding, Measurement Input						0							0
Series B Warrants [Member] | Measurement Input, Price Volatility [Member]
Warrants and Rights Outstanding, Measurement Input						68.8							68.8
Series B Warrants [Member] | Measurement Input, Risk Free Interest Rate [Member]
Warrants and Rights Outstanding, Measurement Input						1.58							1.58
Series A and Series B Warrants [Member]
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share) | $ / shares						$ 1.55							$ 1.55
Warrants and Rights Outstanding | $						$ 4,081,000							$ 4,081,000
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) | $ / shares		$ 1.84								$ 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	9,893,776
Warrants and Rights Outstanding | $															$ 3,502,000	$ 3,502,000
Class of Warrants or Rights, Outstanding, Percentage of Common Stock																15.00%
Class of Warrants and Rights Outstanding, Exercise Price Percentage of Conversion Rate																120.00%
Warrants Issued Upon Conversion of Term Loan with CRG [Member] | Measurement Input, Expected Dividend Rate [Member]
Warrants and Rights Outstanding, Measurement Input																0
Warrants Issued Upon Conversion of Term Loan with CRG [Member] | Measurement Input, Price Volatility [Member]
Warrants and Rights Outstanding, Measurement Input																68.8
Warrants Issued Upon Conversion of Term Loan with CRG [Member] | Measurement Input, Risk Free Interest Rate [Member]
Warrants and Rights Outstanding, Measurement Input																1.58
May 2017 Issuance Related to 2017 Loan Agreement [Member]
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share) | $ / shares		$ 950								$ 950							$ 950
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								2,220							2,220
Warrants and Rights Outstanding | $																	$ 940,000
Share-based Payment Arrangement, Expense | $										$ 0		$ 0
May 2017 Issuance Related to 2017 Loan Agreement [Member] | Measurement Input, Expected Dividend Rate [Member]
Warrants and Rights Outstanding, Measurement Input																	0
May 2017 Issuance Related to 2017 Loan Agreement [Member] | Measurement Input, Price Volatility [Member]
Warrants and Rights Outstanding, Measurement Input																	0.551
May 2017 Issuance Related to 2017 Loan Agreement [Member] | Measurement Input, Risk Free Interest Rate [Member]
Warrants and Rights Outstanding, Measurement Input																	0.0225
May 2017 Issuance Related to 2017 Loan Agreement [Member] | Measurement Input, Expected Term [Member]
Warrants and Rights Outstanding, Measurement Input | yr																	10
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) | $ / shares						$ 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) | $ / shares						$ 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) | $ / shares						$ 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) | $ / shares						$ 1.55							$ 1.55
Warrants and Rights Outstanding, Term (Year)						5 years							5 years
Common Stock [Member]
Stock Issued During Period, Value, Restricted Stock Award, Gross | $
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] | Series B 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) | $ / shares						$ 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) | $ / shares						$ 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