Note 2 - Revenue - Narrative (Details) - USD ($)	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Disaggregation of Revenue [Line Items]
Total revenues	$ 270,827,000	$ 157,170,000	$ 17,812,000
Royalty revenue
Disaggregation of Revenue [Line Items]
Total revenues	2,903,000	(100,000)	3,381,000
Royalty revenue | Torii Pharmaceutical Co., Ltd.
Disaggregation of Revenue [Line Items]
Total revenues	1,944	690
Collaborative and other research and development
Disaggregation of Revenue [Line Items]
Total revenues	214,000	5,920,000	11,130,000
Collaborative and other research and development | U.S. Department of Health and Human Services
Disaggregation of Revenue [Line Items]
Total revenues	190,000	5,920,000	9,231,000
Collaborative and other research and development | Other Collaborators
Disaggregation of Revenue [Line Items]
Total revenues	$ 24,000	$ 0	$ 0