Note 13 - Income Taxes Textual (Details) - USD ($)	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Income Tax Disclosure [Line Items]
Change in valuation allowance	$ 70,894,000	$ 47,954,000	$ 38,551,000
Provisions and accruals for interest and penalties	$ 0	$ 0	$ 0
Open tax year	2018 2019 2020 2021
Research Tax Credit Carryforward
Income Tax Disclosure [Line Items]
Tax credit carryforward, amount	$ 100,165,000
Domestic Tax Authority
Income Tax Disclosure [Line Items]
Operating loss carryforwards, total	408,671,000
State and Local Jurisdiction
Income Tax Disclosure [Line Items]
Operating loss carryforwards, total	188,341,000
Foreign Tax Authority
Income Tax Disclosure [Line Items]
Operating loss carryforwards, total	$ 47,337,000