Note 8 - Income Taxes (Details Textual) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Tax Credit Carryforward, Amount	$ 2,700
Period Of Increase In Ownership (Year)	3 years
Unrecognized Tax Benefits, Ending Balance		$ 0
Domestic Tax Authority [Member]
Operating Loss Carryforwards, Total	$ 83,700
Operating Loss Carryforwards Subject to Expiration	62,700
Operating Loss Carry Forwards Indefinite	21,000
State and Local Jurisdiction [Member]
Operating Loss Carryforwards, Total	$ 12,800