Note 8 - Stockholders' Equity (Details Textual) - USD ($) $ / shares in Units, $ in Thousands					1 Months Ended	3 Months Ended		4 Months Ended
	Mar. 31, 2022	Mar. 25, 2021	Mar. 23, 2021	Sep. 17, 2020	Apr. 30, 2022	Mar. 31, 2022	Mar. 31, 2021	Apr. 30, 2022	May 05, 2022
Proceeds from Issuance of Common Stock						$ 205	$ 570
March 2021 Warrants [Member]
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)			$ 3.60
Warrants and Rights Outstanding, Term (Year)			5 years
March 2021 Public Offering [Member]
Equity Issued During Period, Units, New Issues (in shares)			9,230,500
Units, Number of Securities Called by Each Unit (in shares)			1
Stock and Warrants Issued, Price Per Share (in dollars per share)		$ 3.25
Proceeds from Issuance or Sale of Equity, Gross Amount		$ 30,000
Proceeds from Issuance or Sale of Equity, Total		$ 27,400
ATM Program [Member]
Shares Authorized to Be Offered and Sold Under Offering Agreement, Value				$ 10,000
Stock Issued During Period, Shares, New Issues (in shares)						200,348	105,083
Stock Issued During Period, Value, New Issues						$ 200	$ 600
Proceeds from Issuance of Common Stock	$ 4,800
ATM Program [Member] | Subsequent Event [Member]
Stock Issued During Period, Shares, New Issues (in shares)					936,898			936,898
Stock Issued During Period, Value, New Issues					$ 1,100
Proceeds from Issuance of Common Stock					$ 1,000
Stock Offering Agreement, Remaining Amount Available									$ 3,700
ATM Program [Member] | Ladenburg [Member]
Commission Fee, Percent Fee				3.00%