Note 9 - Preferred Stock (Details Textual) - USD ($)			1 Months Ended					3 Months Ended	12 Months Ended
	Nov. 26, 2019	Nov. 12, 2019	Feb. 29, 2020	Jan. 31, 2020	Dec. 31, 2019		Nov. 30, 2019	Mar. 31, 2020	Dec. 31, 2019
Class of Warrant or Right, Number of Securities Called by Warrants or Rights (in shares)								23,665,905
Warrants Issued Upon Conversion of Term Loan with CRG [Member]
Class of Warrant or Right, Number of Securities Called by Warrants or Rights (in shares)	9,893,776	9,893,776						9,893,776
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 A Preferred Stock [Member]
Convertible Preferred Stock, Shares Issued upon Conversion (in shares)							1	1
Preferred Stock, Shares Outstanding, Ending Balance (in shares)					1,852,173	[1]		0	1,852,173	[1]
Series A Convertible Preferred Stock [Member]
Preferred Stock, Shares Outstanding, Ending Balance (in shares)								0
Series B Preferred Stock [Member]
Preferred Stock, Shares Outstanding, Ending Balance (in shares)					31,678	[1]		32,667	31,678	[1]
Preferred Stock, Dividend Rate, Percentage	12.50%
Preferred Stock Dividends, Shares (in shares)								989	378
Dividends, Preferred Stock, Cash								$ 1,000	$ 2,400
Preferred Stock, Fair Value, Per Share (in dollars per share)	$ 1,023.23
Convertible Preferred Stock, Fair Value	$ 32,027,000
Stock Issued During Period, Shares, Conversion of Convertible Securities (in shares)	31,300

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