Note 6 - Stockholders' Equity (Details Textual) - USD ($) $ / shares in Units, $ in Thousands			2 Months Ended	9 Months Ended
	Jul. 02, 2021	Sep. 01, 2020	Mar. 23, 2021	Sep. 30, 2021	Sep. 30, 2020
Proceeds from Issuance of Common Stock, Net				$ 9,053
Stock Issued During Period, Shares, Exercise of Warrants for Cash (in shares)			228,938	228,939
Proceeds from Warrant Exercises			$ 1,000	$ 1,042	$ 52
Stock Issued During Period, Shares, Cashless Exercise of Warrants (in shares)				190,588
Class of Warrant or Right, Exercised During Period (in shares)				536,140
Warrants With Exercise Price of $5.00 [Member]
Class of Warrants or Rights, Cancelled During the Period (in shares)				573,339
Class of Warrant or Right, Cancelled During Period, Exercise Price (in dollars per share)				$ 5.00
Warrants With Exercise Price of $15.00 [Member]
Class of Warrants or Rights, Cancelled During the Period (in shares)				108,550
Class of Warrant or Right, Cancelled During Period, Exercise Price (in dollars per share)				$ 15.00
Underwritten Warrants [Member]
Warrants and Rights Outstanding, Term (Year)		5 years
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)		$ 4.54
Class of Warrant or Right, Number of Securities Called by Warrants or Rights (in shares)				2,306,516
Underwritten Public Offering [Member]
Stock Issued During Period, Shares, New Issues (in shares)	3,333,334	2,545,454
Shares Issued, Price Per Share (in dollars per share)	$ 3.00
Proceeds from Issuance of Common Stock	$ 10,000
Proceeds from Issuance of Common Stock, Net	$ 9,100
Proceeds from Issuance or Sale of Equity, Total		$ 10,500
Proceeds from Issuance of Common Stock, Net		$ 9,300			$ 9,335