Note 2 - Liquidity and Capital Resources (Details Textual) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2022	Mar. 31, 2022	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2022	Jun. 30, 2021	Dec. 31, 2021
Net Income (Loss) Attributable to Parent, Total	$ (6,672)	$ (4,785)	$ (7,039)	$ (3,538)	$ (11,457)	$ (10,577)
Net Cash Provided by (Used in) Operating Activities, Total					(10,827)	(9,745)
Cash and Cash Equivalents, at Carrying Value, Total	125,537		$ 142,433		125,537	$ 142,433	$ 136,377
Working Capital (Deficit)	$ 129,629				$ 129,629