Note 7 - Stockholders' Equity (Details Textual)					12 Months Ended
	Feb. 11, 2021 USD ($) $ / shares shares	Sep. 23, 2020 USD ($) $ / shares shares	Aug. 13, 2020 USD ($) shares	Nov. 11, 2019 $ / shares shares	Dec. 31, 2021 USD ($) $ / shares	Dec. 31, 2020 USD ($) $ / shares	Dec. 31, 2019 $ / shares
Debt Conversion, Accrued Interest, Amount | $					$ 0
Gain (Loss) on Extinguishment of Debt, Total | $					$ 1,964,000	$ (0)
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)					$ 3.57	$ 3.73	$ 3.34
Warrant Issued in connection with Conversion of Subordinated Debt [Member]
Class of Warrant or Right, Number of Securities Called by Each Warrant or Right (in shares) | shares	150,418
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)	$ 2.507
Class of Warrant or Right, Grant Date Fair Value (in dollars per share)	$ 2.02
Class of Warrant or Right, Period Following Issuance at which Warrants are Exercisable (Year)	1 year
Warrants and Rights Outstanding | $	$ 304,000
Warrant In Connection With Amended Subordinated Loan [Member]
Class of Warrant or Right, Number of Securities Called by Each Warrant or Right (in shares) | shares				41,667
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)				$ 3.00
Class of Warrant or Right, Grants in Period, Grant Date Fair Value (in dollars per share)				$ 2.40
Warrant Issued in Connection with Amended 2017 Credit Agreement [Member]
Class of Warrant or Right, Number of Securities Called by Each Warrant or Right (in shares) | shares		1,000,000
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)		$ 3.75
Class of Warrant or Right, Period Following Issuance at which Warrants are Exercisable (Year)		1 year
Warrants and Rights Outstanding | $		$ 1,400,000
Class of Warrant or Right, Grants in Period, Grant Date Fair Value (in dollars per share)		$ 1.42
Warrants and Rights Outstanding, Term (Year)		5 years
Warrants Issued in Connection With the Conversion of Subordinated Loan Agreement to Common Stock [Member]
Class of Warrant or Right, Number of Securities Called by Each Warrant or Right (in shares) | shares	150,418
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)	$ 2.507
Class of Warrant or Right, Period Following Issuance at which Warrants are Exercisable (Year)	1 year
Class of Warrant or Right, Grants in Period, Grant Date Fair Value (in dollars per share)	$ 2.02
Class of Warrant or Right, Number of Warrants Grants in Period, Gross	1
Warrants and Rights Outstanding, Term (Year)	5 years
Subordinated Debt [Member]
Gain (Loss) on Extinguishment of Debt, Total | $			$ 552,000
Conversion from Subordinated Promissory Note to Common Stock [Member]
Debt Conversion, Original Debt, Percentage of Total Debt	50.00%		50.00%
Debt Conversion, Original Debt, Amount | $	$ 1,250,000		$ 1,250,000
Debt Conversion, Accrued Interest, Amount | $	$ 62,000		$ 265,000
Debt Conversion, Converted Instrument, Shares Issued (in shares) | shares	601,674		403,602
Debt Conversion, Converted Instrument, Amount | $			$ 963,000