Note 12 - Income Taxes (Details Textual) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Income Tax Expense (Benefit)	$ 0	$ 0
Deferred Tax Liabilities, Net, Total	0	0
Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount	2,700	2,900
Unrecognized Tax Benefits that Would Impact Effective Tax Rate	1,200	$ 1,100
Domestic Tax Authority [Member] | Internal Revenue Service (IRS) [Member]
Operating Loss Carryforwards	113,500
Domestic Tax Authority [Member] | Internal Revenue Service (IRS) [Member] | Research Tax Credit Carryforward [Member]
Tax Credit Carryforward, Amount	3,900
State and Local Jurisdiction [Member]
Operating Loss Carryforwards	65,200
State and Local Jurisdiction [Member] | Research Tax Credit Carryforward [Member]
Tax Credit Carryforward, Amount	$ 2,800