Note 8 - Income Taxes (Details Textual) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Tax Credit Carryforward, Amount	$ 3,100
Period Of Increase In Ownership (Year)	3 years
Unrecognized Tax Benefits, Ending Balance	$ 0	$ 0
Domestic Tax Authority [Member]
Operating Loss Carryforwards, Total	11,100
Operating Loss Carry Forwards Indefinite	17,600
State and Local Jurisdiction [Member]
Operating Loss Carryforwards, Total	$ 62,700