Note 3 - Collaborative and Other Research and Development Contracts (Details Textual) - USD ($) $ in Thousands			1 Months Ended			3 Months Ended	46 Months Ended	48 Months Ended
	Jun. 16, 2015	Feb. 28, 2006	Sep. 30, 2013	Jun. 30, 2006	Jun. 30, 2000	Mar. 31, 2019	Mar. 31, 2019	Mar. 31, 2019	Mar. 31, 2015	Nov. 11, 2011
CSL Limited [Member
Proceeds from License Fees Received	$ 33,740
Milestone Payment Received							$ 12,000
Royalty Term	10 years
Base Contract [Member]
Government Contract Receivable									$ 16,265
Additional Development Options [Member]
Government Contract Receivable									22,855
ASPRBARDA Contract [Member]
Government Contract Receivable									$ 39,120
Proceeds from awards for Research and Development Contracts								$ 20,574
Green Cross Corporation [Member]
Proceeds from License Fees Received				$ 250
Mundipharma [Member]
Upfront Payments Receivable Amount		$ 10,000
Potential Milestone Payments Receivable										$ 15,000
AECOM and IRL [Member]
Milestone Payment Minimum					$ 1,400
Milestone Payment Maximum					4,000
Annual License Fee Minimum					150
Annual License Fee Maximum					$ 500
Advance Notice Period for Termination of Agreement					60 days
National Institute of Allergy and Infectious Diseases [Member]
Collaborative Agreement Contract Value			$ 5,000
Expected Receivable From Awards for Research and Development Contracts						$ 43,035
UAB [Member]
Period of Agreement						25 years
Renewable Period of Agreement						5 years