Note 2 - Summary of Significant Accounting Policies (Details Textual)		3 Months Ended	12 Months Ended
	Jan. 01, 2019 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Jan. 01, 2018 USD ($)	Dec. 31, 2017 USD ($)
Receivables Percentage			100.00%	100.00%
Accounts Receivable, Allowance for Credit Loss, Ending Balance			$ 0	$ 0
Retained Earnings (Accumulated Deficit), Ending Balance			(95,192,881)	(123,032,408)
Revenue from Contract with Customer, Excluding Assessed Tax, Total			124,959,304	26,742,085	$ 477,053,782
Contract with Customer, Receivable, after Allowance for Credit Loss, Current, Total			1,300,000
Contract with Customer, Liability, Revenue Recognized			100,000
Revenue, Remaining Performance Obligation, Amount			63,500,000
Operating Lease, Right-of-Use Asset			$ 2,944,932	2,944,932
Number of Operating Segments			1
Number of Reporting Units			1
Cash and Cash Equivalents, at Carrying Value, Ending Balance			$ 117,890,240	65,249,072	100,652,809		$ 19,857,833
Number of Reportable Segments			1
Fair Value, Inputs, Level 1 [Member]
Cash and Cash Equivalents, at Carrying Value, Ending Balance			$ 100,000
Restricted Cash and Cash Equivalents, Total				5,600,000
Fair Value, Inputs, Level 2 [Member]
Restricted Cash and Cash Equivalents, Total				90,000,000.0
The IV Formulation R & D Contract with BARDA [Member] | Transferred over Time [Member]
Contract with Customer, Asset, Cumulative Catch-up Adjustment to Revenue, Change in Estimate of Transaction Price		$ 3,300,000		3,300,000
Contract with Customer, Liability, Revenue Recognized			$ 1,400,000	$ 7,500,000
Accounting Standards Update 2014-09 [Member]
Deferred Revenue, Total						$ 1,800,000
Deferred Costs, Total						2,100,000
Accounts Receivable, after Allowance for Credit Loss, Total						100,000
Retained Earnings (Accumulated Deficit), Ending Balance						$ 200,000
Revenue from Contract with Customer, Excluding Assessed Tax, Total					$ 1,000,000.0
Accounting Standards Update 2016-02 [Member]
Operating Lease, Right-of-Use Asset	$ 2,900,000
Operating Lease, Liability, Total	3,300,000
Increase (Decrease) in Deferred Rent	$ 400,000
Laboratory Equipment [Member]
Property, Plant and Equipment, Useful Life (Year)			5 years
Computer Equipment [Member]
Property, Plant and Equipment, Useful Life (Year)			3 years
Furniture and Fixtures [Member]
Property, Plant and Equipment, Useful Life (Year)			7 years