Note 1 - Significant Accounting Policies - Summary of Revenues (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2019
Revenues	$ 40,994	$ 6,102	$ 110,012	$ 13,796
Torii Pharmaceutical Co. [Member]
Revenues			1,617		$ 20,101
Product [Member]
Revenues	39,141	2,478	90,442	2,696
Product [Member] | ORLADEYO [Member]
Revenues	36,711	0	76,023	0
Product [Member] | RAPIVAB [Member]
Revenues	2,430	11	7,165	11
Product [Member] | PERAMIVIR [Member]
Revenues	0	2,467	7,254	2,685
Royalty [Member]
Revenues	322	254	(447)	2,243
Milestone [Member]
Revenues	0	0	15,000	0
Collaborative and Other Research and Development [Member]
Revenues	1,531	3,370	5,017	8,857
Collaborative and Other Research and Development [Member] | US Department of Health and Human Services [Member]
Revenues	1,531	3,088	5,017	7,240
Collaborative and Other Research and Development [Member] | Torii Pharmaceutical Co. [Member]
Revenues	$ 0	$ 282	$ 0	$ 1,617