Note 3 - Income Taxes (Details Textual) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021	Dec. 31, 2021
Income Tax Expense (Benefit), Total	$ 0	$ 0	$ (0)	$ 0
Deferred Tax Assets, Valuation Allowance					$ 117,300
Unrecognized Tax Benefits, Income Tax Penalties and Interest Accrued, Total	$ 0		$ 0
Open Tax Year			2014 2015 2016 2017 2018 2019 2020 2021
Pre 2018 [Member] | Domestic Tax Authority [Member] | Internal Revenue Service (IRS) [Member]
Operating Loss Carryforwards					245,200
Post 2017 [Member] | Domestic Tax Authority [Member] | Internal Revenue Service (IRS) [Member]
Operating Loss Carryforwards					$ 190,800
Earliest Tax Year [Member]
Operating Loss Carryforwards, Expiration Date					Dec. 31, 2022
Latest Tax Year [Member]
Operating Loss Carryforwards, Expiration Date					Dec. 31, 2037