Note 9 - Stockholders' Equity (Details Textual) - USD ($)				3 Months Ended
	Mar. 22, 2021	Jan. 08, 2021	Jan. 06, 2021	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021	Dec. 21, 2020	Dec. 17, 2020
Number of Shares Authorized to Issue (in shares)				185,000,000
Common Stock, Shares Authorized (in shares)				175,000,000		175,000,000
Common Stock, Par or Stated Value Per Share (in dollars per share)				$ 0.18		$ 0.18
Preferred Stock, Shares Authorized (in shares)				10,000,000		10,000,000
Preferred Stock, Par or Stated Value Per Share (in dollars per share)				$ 0.001		$ 0.001
Preferred Stock, Shares Issued (in shares)				1,000		1,000
Consummate a Business Combination, Percentage of Acquired Outstanding Shares				50.00%
Consummate a Business Combination, Percentage of Aggregate Ordinary Voting Power				50.00%
Class of Warrant or Right, Outstanding (in shares)				22,277,000
Class of Warrant or Right, Exercised During Period (in shares)				0	32,063,000
Proceeds from Warrant Exercises				$ 0	$ 32,760,000
Stock Issued During Period, Shares, Warrant Exercised (in shares)					32,063,000
Conversion of Series B Convertible Preferred Stock into Common Stock [Member]
Conversion of Stock, Shares Converted (in shares)				0	1.000
Conversion of Stock, Shares Issued (in shares)					285
The 2021 Financing Transaction Warrants [Member]
Class of Warrant or Right, Number of Securities Called by Each Warrant or Right (in shares)	0.75					1
Warrants and Rights Outstanding, Term (Year)	4 years 6 months
Shares Issuable Upon Exercise of Warrants (in shares)	13,021,000
Warrants Associated with 2020 Offering Consisting of Common Stock and Warrants [Member] | Minimum [Member]
Warrants and Rights Outstanding, Term (Year)								4 years
Warrants Associated with 2020 Offering Consisting of Common Stock and Warrants [Member] | Maximum [Member]
Warrants and Rights Outstanding, Term (Year)								4 years 6 months
The 2020 Warrants [Member]
Class of Warrant or Right, Number of Securities Called by Each Warrant or Right (in shares)							1
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)				$ 1.00
Warrants Exercisable, Ownership Percentage of Company’s Shares Allowed							4.99%
Common Stock, Convertible, Ownership Percentage of Company’s Shares Allowed							9.99%
Class of Warrant or Right, Outstanding (in shares)				6,490,000
The 2021 Financing Transaction [Member]
Common Stock, Par or Stated Value Per Share (in dollars per share)	$ 0.18		$ 0.18
Stock Issued During Period, Shares, New Issues (in shares)	17,361,000		23,850,000
Class of Warrant or Right, Number of Securities Called by Warrants or Rights (in shares)	13,021,000
Issuance of Common Stock and Warrants, Combined Purchase Price Per Share (in dollars per share)			$ 1.055
Proceeds From Issuance of Common Stock and Warrants, Net of Issuance Costs	$ 46,400,000	$ 23,300,000
Shares Issued, Price Per Share (in dollars per share)	$ 2.88
The 2021 Financing Transaction [Member] | The 2021 Financing Transaction Warrants [Member]
Class of Warrant or Right, Number of Securities Called by Warrants or Rights (in shares)			17,888,000
Class of Warrant or Right, Number of Securities Called by Each Warrant or Right (in shares)			0.75
Warrants and Rights Outstanding, Term (Year)			4 years 6 months
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)			$ 1.055
Series A Junior Participating Preferred Stock [Member]
Preferred Stock, Shares Authorized (in shares)				750,000
Preferred Stock, Par or Stated Value Per Share (in dollars per share)				$ 0.001
Preferred Stock, Shares Issued (in shares)				0		0
Series A Convertible Preferred Stock [Member]
Preferred Stock, Shares Authorized (in shares)				4,000
Preferred Stock, Par or Stated Value Per Share (in dollars per share)				$ 0.001
Preferred Stock, Shares Issued (in shares)				0		0
Series B Convertible Preferred Stock [Member]
Preferred Stock, Shares Authorized (in shares)				25,000
Preferred Stock, Par or Stated Value Per Share (in dollars per share)				$ 0.001
Stated Value per Share				$ 1,000
Preferred Stock, Convertible, Conversion Price (in dollars per share)				$ 3.52
Preferred Stock, Convertible, Ownership Percentage of Company’s Shares Allowed				9.99%
Series C Convertible Preferred Stock [Member]
Preferred Stock, Shares Authorized (in shares)				20,000
Preferred Stock, Par or Stated Value Per Share (in dollars per share)				$ 0.001
Preferred Stock, Shares Issued (in shares)				0		0