Note 6 - Liabilities Related to Sale of Future Royalties - Deferred Revenue Activity (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2022	Dec. 31, 2021
Current portion	$ (1,369)	$ (836)
Long-term portion	10,664	$ 10,686
HealthCare Royalty Partners III, L.P. [Member] | Royalty Arrangement [Member]
Total liability related to sale of future royalties, start of period	11,522
Non-cash royalty revenue paid to HCRP	(152)
Non-cash interest expense recognized	663
Total liability related to sale of future royalties, end of period	12,033
Current portion	(1,369)
Long-term portion	$ 10,664