Note 2 - Liquidity and Capital Resources (Details Textual) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2022	Sep. 30, 2021	Dec. 31, 2021
Net Income (Loss) Attributable to Parent, Total	$ (8,011)	$ (6,672)	$ (4,786)	$ (5,197)	$ (7,039)	$ (3,538)	$ (19,469)	$ (15,774)
Net Cash Provided by (Used in) Operating Activities, Total							(16,237)	(12,807)
Cash and Cash Equivalents, at Carrying Value, Total	117,367			$ 140,041			117,367	$ 140,041	$ 136,377
Working Capital (Deficit)	$ 120,527						$ 120,527