Note 6 - Liabilities Related to Sale of Future Royalties - Deferred Revenue Activity (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2023	Dec. 31, 2022
Current portion	$ (1,342)	$ (95)
Long-term portion	4,633	$ 5,621
HealthCare Royalty Partners III, L.P. [Member] | Royalty Arrangement [Member]
Total liability related to sale of future royalties, start of period	5,716
Non-cash royalty revenue paid to HCRP	(314)
Non-cash interest expense recognized	573
Total liability related to sale of future royalties, end of period	5,975
Current portion	(1,342)
Long-term portion	$ 4,633