Note 10 - Preferred Stock (Details Textual)				3 Months Ended		28 Months Ended
	Jan. 19, 2021 shares	Nov. 26, 2019 shares	Nov. 12, 2019 shares	Mar. 31, 2022 USD ($) $ / shares shares	Mar. 31, 2021 USD ($) shares	Mar. 31, 2022 USD ($) $ / shares shares	May 15, 2022 shares	Mar. 14, 2022 shares	Dec. 31, 2021 shares	Jan. 31, 2021 shares
Class of Warrant or Right, Number of Securities Called by Warrants or Rights (in shares)				9,793,599		9,793,599
Preferred Stock, Shares Authorized (in shares)				10,000,000		10,000,000			10,000,000
Series B Preferred Stock [Member]
Preferred Stock, Dividend Rate, Percentage		12.50%
Preferred Stock Dividends, Shares (in shares)				1,263	1,118	10,467
Dividends, Preferred Stock, Cash | $				$ 3,000	$ 1,000	$ 19,000
Preferred Stock, Shares Outstanding, Ending Balance (in shares)				41,767	36,937	41,767			40,504
Convertible Preferred Stock, Shares Issued upon Conversion (in shares)		2,729,869		2,729,869	2,414,283	2,729,869			2,647,320
Series B Preferred Stock [Member] | Conversion From Series B Preferred Stock to Common Stock [Member]
Preferred Stock, Convertible, Conversion Ratio				65.36		65.36
Preferred Stock, Liquidation Preference Per Share (in dollars per share) | $ / shares				$ 1,000		$ 1,000
Preferred Stock, Convertible, Conversion Price (in dollars per share) | $ / shares				$ 15.30		$ 15.30
Series C Preferred Stock [Member]
Preferred Stock, Shares Outstanding, Ending Balance (in shares)				0		0		0	0	0
Convertible Preferred Stock, Shares Issued upon Conversion (in shares)				1		1
Preferred Stock, Shares Authorized (in shares)								2,450,880
Series C Preferred Stock [Member] | Subsequent Event [Member]
Preferred Stock, Shares Authorized (in shares)							2,450,880
Series C Preferred Stock [Member] | January 2021 Offering [Member]
Convertible Preferred Stock, Shares Issued upon Conversion (in shares)					1
Stock Issued During Period, Shares, New Issues (in shares)	2,450,880
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)			989,379
Conversion of Term Loan with CRG Into Series B Convertible Preferred Stock [Member]
Debt Conversion, Converted Instrument, Shares Issued (in shares)			31,300