Note 3 - Business Combination - Allocation of the Purchase Price to the Fair Value of the Respective Assets and Liabilities Acquired (Details) - USD ($) $ in Thousands			12 Months Ended
		Feb. 13, 2018	Dec. 31, 2019	Dec. 31, 2018
Cash and cash equivalents				$ 25,525
Accounts receivable				14,666
Prepaid expenses				436
Property and equipment				170
Intangible assets:
Developed technology (1)	[1]			22,100
In-process research and development (2)	[2]			1,600
Total assets				64,497
Accounts payable				(3,304)
Other current liabilities				(6,744)
Liability related to the sale of future royalties				(15,900)
Net assets acquired				38,549
Purchase price		$ (31,789)		(31,789)
Bargain purchase gain (3)				6,760	[3]
Previously Reported [Member]
Cash and cash equivalents		25,525
Accounts receivable		14,666
Prepaid expenses		446
Property and equipment		170
Intangible assets:
Developed technology (1)	[1]	22,400
In-process research and development (2)	[2]	1,600
Total assets		64,807
Accounts payable		(3,379)
Other current liabilities		(6,351)
Liability related to the sale of future royalties		(16,300)
Net assets acquired		38,777
Purchase price		(31,789)
Bargain purchase gain (3)	[3]	$ 6,988
Restatement Adjustment [Member]
Cash and cash equivalents
Accounts receivable
Prepaid expenses				(10)
Property and equipment
Intangible assets:
Developed technology (1)	[1]			(300)
In-process research and development (2)	[2]
Total assets				(310)
Accounts payable				75
Other current liabilities				(393)
Liability related to the sale of future royalties				400
Net assets acquired				(228)
Purchase price
Bargain purchase gain (3)	[3]			$ (228)

[1] Developed technology comprises Inavir and Relenza, both influenza vaccines on which the Company is presently receiving royalty revenue, which, based on valuations prepared by an independent third party based on estimated discounted cash flows based on probability-weighted future development expenditures and revenue streams provided by the Company's management, are being amortized on a straight-line basis over the estimated periods of future royalties of 11.75 and 1.3 years, respectively.

[2] In-process research and development (see Note 5) related to teslexivir, or BTA074, a direct-acting antiviral that, at the time of the Merger, was being actively developed as a treatment for genital warts. The valuation was prepared by an independent third party based on estimated discounted cash flows based on probability-weighted future development expenditures and revenue streams provided by the Company's management.

[3] The bargain purchase gain represents the excess of the fair value of tangible and identified intangible assets acquired, less liabilities assumed, over the purchase price.