Note 1 - Significant Accounting Policies - Summary of Revenues (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2019
Revenues	$ 19,059	$ 4,823
Torii Pharmaceutical Co. [Member]
Revenues		1,053	$ 20,101
Product [Member]
Revenues	17,871	218
Product [Member] | ORLADEYO [Member]
Revenues	10,938	0
Product [Member] | PERAMIVIR [Member]
Revenues	6,820	218
Product [Member] | RAPIVAB [Member]
Revenues	113	0
Royalty [Member]
Revenues	(897)	1,945
Collaborative and Other Research and Development [Member]
Revenues	2,085	2,660
Collaborative and Other Research and Development [Member] | US Department of Health and Human Services [Member]
Revenues	2,085	1,607
Collaborative and Other Research and Development [Member] | Torii Pharmaceutical Co. [Member]
Revenues	$ 0	$ 1,053