Note 7 - Stockholders' Equity (Details Textual) $ / shares in Units, $ in Millions				3 Months Ended
	Mar. 05, 2024 shares	Mar. 04, 2024 $ / shares shares	Aug. 02, 2023 $ / shares shares	Mar. 31, 2024 USD ($) $ / shares shares	Mar. 31, 2023 shares	Dec. 31, 2023 $ / shares shares	Dec. 23, 2023 shares	Sep. 30, 2023 $ / shares shares	Dec. 31, 2022 $ / shares shares	Jan. 14, 2022 $ / shares shares	Feb. 16, 2018 $ / shares
Preferred Stock, Shares Authorized (in shares)				5,000,000		5,000,000		5,000,000	5,000,000
Preferred Stock, Par or Stated Value Per Share | $ / shares				$ 0.001		$ 0.001			$ 0.001
Preferred Stock, Shares Outstanding (in shares)				19,229		62,881
Preferred Stock, Shares Issued				19,229		62,881
Securities Purchase Agreement, Number of Shares to Convert	10,000
Common Stock, Shares Authorized				100,000,000		100,000,000
Common Stock, Par or Stated Value Per Share (in dollars per share) | $ / shares		$ 0.001		$ 0.001				$ 0.001	$ 0.001
Common Stock, Shares, Outstanding, Ending Balance (in shares)				1,586,434		1,279,928
Common Stock, Shares, Issued (in shares)				1,586,434		1,279,928
Class of Warrant or Right, Number of Securities Called by Warrants or Rights		40,938		497,034		456,096	456,096
Common Warrants [Member]
Class of Warrant or Right, Number of Securities Called by Warrants or Rights										40,938
Class of Warrant or Right, Exercise Price of Warrants or Rights | $ / shares										$ 3.664
Warrants and Rights Outstanding, Term										5 years
March 2024 Offering [Member]
Stock Issued During Period, Shares, New Issues	75,327
Common Stock [Member]
Shares Issued, Price Per Share | $ / shares		$ 3.664		$ 3.664
Stock Issued During Period, Shares, New Issues		75,327			794
Series A Preferred Stock [Member]
Preferred Stock, Shares Outstanding (in shares)				60,876					60,876
Series A-1 Preferred Stock [Member]
Preferred Stock, Shares Authorized (in shares)				10,000
Preferred Stock, Excess Fair Value | $				$ 1.9
Preferred Stock, Stated Value | $ / shares				$ 1,000
Preferred Stock, Convertible, Conversion Ratio				273
Preferred Stock, Convertible, Shares Issuable	2,729,257			2,729,257
Securities Purchase Agreement, Number of Shares to Convert				10,000
Series B Preferred Stock [Member]
Preferred Stock, Par or Stated Value Per Share | $ / shares											$ 0.001
Preferred Stock, Shares Outstanding (in shares)								85	85
Preferred Stock, Convertible, Conversion Price (in dollars per share) | $ / shares								$ 3.664	$ 3.664
Series E Preferred Stock [Member]
Preferred Stock, Par or Stated Value Per Share | $ / shares			$ 1,000
Preferred Stock, Shares Outstanding (in shares)								1,920
Preferred Stock, Convertible, Conversion Ratio			93
Preferred Stock, Convertible, Shares Issuable			178,560
Preferred Stock, Convertible, Conversion Price (in dollars per share) | $ / shares			$ 10.725
Preferred Stock, Convertible, Beneficial Ownership Percentage			19.99%
Preferred Stock, Dividend Rate, Percentage			8.00%
Dividends, Preferred Stock | $				$ 0.1
Series F Preferred Stock [Member]
Preferred Stock, Par or Stated Value Per Share | $ / shares		$ 0.001
Preferred Stock, Shares Outstanding (in shares)				7,224
Preferred Stock, Stated Value | $ / shares		$ 1,000
Preferred Stock, Convertible, Conversion Ratio		273
Shares Issued, Price Per Share | $ / shares		$ 1,000
Preferred Stock, Convertible, Beneficial Ownership Percentage		19.90%
Preferred Stock, Dividend Rate, Percentage		5.00%
Dividends, Preferred Stock | $				$ 0.1
Stock Issued During Period, Shares, New Issues		7,224
Preferred Stock Dividend Rate, Percentage, Thereafter Third Anniversary Of Issuance		8.00%
Series F Convertible Preferred Stock [Member]
Preferred Stock, Convertible, Shares Issuable		1,971,616
Series D Preferred Stock [Member] | January 2022 offering [Member] | Common Warrants [Member]
Conversion of Warrants Allowed Maximum Ownership of Common Stock Percentage										4.99%
Conversion of Warrants Allowed Maximum Ownership of Common Stock Percentage upon Election										9.99%