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, 2020	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 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 sale of future royalties		(16,300)
Net assets acquired		38,777
Purchase price		(31,789)
Bargain purchase gain (3)	[3]	$ 6,988
Revision of Prior Period, 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 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, or was, 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, or has been, amortized on a straight-line basis over the estimated periods of future royalties at the time of the acquisition 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.