Note 9 - Income Taxes (Details Textual) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Deferred Tax Assets, Valuation Allowance	$ 418,317	$ 400,363
Current Income Tax Expense (Benefit)	$ 400
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent	21.00%
Domestic Tax Authority [Member]
Deferred Tax Liabilities, Deferred Expense, Capitalized Research and Development Costs	$ 61,800
Operating Loss Carryforwards	1,400,000
Domestic Tax Authority [Member] | Research Tax Credit Carryforward [Member]
Tax Credit Carryforward, Amount	45,800
Domestic Tax Authority [Member] | Business Interest Expense Carryforward [Member]
Tax Credit Carryforward, Amount	14,500
Foreign Tax Authority [Member]
Deferred Tax Liabilities, Deferred Expense, Capitalized Research and Development Costs	$ 13,900