Note 4 - Income Taxes (Details Textual) $ in Thousands	3 Months Ended
	Mar. 31, 2022 USD ($)
Unrecognized Tax Benefits, Ending Balance	$ 900
Unrecognized Tax Benefits that Would Impact Effective Tax Rate	0
Deferred Tax Assets, Net, Total	0
Domestic Tax Authority [Member] | Internal Revenue Service (IRS) [Member]
Operating Loss Carryforwards	$ 334,000
Open Tax Year	2018 2019 2020 2021
Open Tax Period (Year)	3 years
Domestic Tax Authority [Member] | California Franchise Tax Board [Member]
Operating Loss Carryforwards	$ 268,000
Open Tax Year	2017 2018 2019 2020 2021
State and Local Jurisdiction [Member] | California Franchise Tax Board [Member]
Open Tax Period (Year)	4 years