Note 13 - Income Taxes (Details Textual) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2019	Dec. 31, 2021
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent	21.00%	21.00%	21.00%
Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount	$ 16,200	$ 23,700
Unrecognized Tax Benefits, Ending Balance	6,566	4,945		$ 2,422
Unrecognized Tax Benefits, Income Tax Penalties and Interest Expense, Total	0	0
Domestic Tax Authority [Member]
Operating Loss Carryforwards	201,100	162,100
Operating Loss Carryforwards, Subject to Expiration	1,800
Operating Loss Carryforward, Carried Forward Indefinitely	199,300
Domestic Tax Authority [Member] | Research Tax Credit Carryforward [Member]
Tax Credit Carryforward, Amount	9,400	6,900
State and Local Jurisdiction [Member]
Operating Loss Carryforwards	87,500	85,000
Operating Loss Carryforwards, Subject to Expiration	2,900
Operating Loss Carryforward, Carried Forward Indefinitely	$ 84,600
Open Tax Year	2016 2017 2018 2019 2020 2021
State and Local Jurisdiction [Member] | Research Tax Credit Carryforward [Member]
Tax Credit Carryforward, Amount	$ 8,500	$ 7,000
Foreign Tax Authority [Member] | Australian Taxation Office [Member]
Operating Loss Carryforwards	$ 4,900