Note 1 - Organization and Summary of Significant Accounting Policies (Details Textual) $ in Thousands |
1 Months Ended | 12 Months Ended | 75 Months Ended | |||
|---|---|---|---|---|---|---|
Mar. 16, 2020 |
Sep. 18, 2015
USD ($)
|
Sep. 30, 2015
USD ($)
|
Dec. 31, 2021
USD ($)
|
Dec. 31, 2020
USD ($)
|
Dec. 31, 2021
USD ($)
|
|
| Cash, Cash Equivalents, and Short-term Investments, Total | $ 51,630 | $ 42,886 | $ 51,630 | |||
| Restructuring and Related Cost, Number of Positions Eliminated | 30 | |||||
| Restructuring Charges, Total | $ 500 | |||||
| Proceeds From Sale of Royalty and Milestone Rights | $ 65,000 | $ 65,000 | ||||
| Royalty Arrangment Maximum Payments | 195,000 | 195,000 | ||||
| Net Proceeds from Sale of Future Royalties | $ 61,200 | $ 61,200 | $ 0 | $ 61,184 | ||
| Minimum [Member] | ||||||
| Property, Plant and Equipment, Useful Life (Year) | 3 years | |||||
| Maximum [Member] | ||||||
| Property, Plant and Equipment, Useful Life (Year) | 5 years | |||||