Note 1 - Significant Accounting Policies - Summary of Revenues (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Revenues	$ 1,448	$ 12,494	$ 7,335	$ 16,470
Product [Member]
Revenues			1,679
Royalty [Member]
Revenues	696	142	3,018	3,803
Collaborative and Other Research and Development [Member]
Revenues	752	12,352	2,638	12,667
Collaborative and Other Research and Development [Member] | US Department of Health and Human Services [Member]
Revenues	752	352	2,638	667
Collaborative and Other Research and Development [Member] | Seqirus UK Limited [Member]
Revenues		$ 12,000		$ 12,000