Note 9 - Shareholders' Equity (Details Textual) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2021	Sep. 30, 2020	Aug. 31, 2021
Proceeds from Issuance of Common Stock		$ 389	$ 0
Stock Issued During Period, Exercise Of Warrants, Shares (in shares)	1,500
Common Stock Purchase Agreement With Nineteenth Investment Company LLC [Member]
Stock Dividends, Shares, Total (in shares)	399	798
ATM Sales Agreement [Member]
Aggregate Proceeds, Common Stock Sales				$ 50,000
Stock Issued During Period, Shares, New Issues (in shares)	100	100
Proceeds from Issuance of Common Stock	$ 400	$ 400