Note 11 - Income Taxes (Details Textual) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2023 USD ($) $ / shares shares	Mar. 31, 2022 USD ($)
Income Tax Expense (Benefit)	$ 23	$ 7
Operating Loss Carryforwards	288,462
Operating Loss Carryforwards, Subject to Expiration	227,781
Operating Loss Carry Forwards Annual Limit	14,284
Unrecognized Tax Benefits	0
Unrecognized Tax Benefits, Income Tax Penalties and Interest Accrued	$ 0
Rights [Member]
Term of Extended Rights Plan (Year)	3 years
Threshold Percentage of Beneficial Ownership for Significant Dilution in Ownership Interest	4.90%
Class of Warrant or Right Number of Rights Per Common Stock Share	1
Class of Warrant or Right, Number of Securities Called by Each Warrant or Right (in shares) | shares	0.001
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share) | $ / shares	$ 7.26
Class of Warrant or Right Current Beneficial Ownership Percentage That Will Not Trigger Preferred Share Purchase Rights	4.90%