Note 12 - Income Taxes (Details Textual) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount	$ 15,800
Unrecognized Tax Benefits	715	$ 335	$ 141
Unrecognized Tax Benefits, Income Tax Penalties and Interest Accrued	$ 0	$ 0
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent	21.00%	21.00%
Domestic Tax Authority [Member]
Operating Loss Carryforwards	$ 446,700
Increase (Decrease) in Operating Loss Carryforwards	253,000
Operating Loss Carryforwards, Subject to Expiration	254,500
Operating Loss Carryforwards, Not Subject to Expiration	192,200
Domestic Tax Authority [Member] | Research Tax Credit Carryforward [Member]
Tax Credit Carryforward, Amount	11,700
Increase (Decrease) in Tax Credit Carryforward	8,800
State and Local Jurisdiction [Member]
Operating Loss Carryforwards	336,300
Operating Loss Carryforwards, Subject to Expiration	323,000
Operating Loss Carryforwards, Not Subject to Expiration	13,300
State and Local Jurisdiction [Member] | Impact of 382 Ownership Changes [Member]
Increase (Decrease) in Operating Loss Carryforwards	199,000
Foreign Tax Authority [Member] | Ministry of Economic Affairs and Finance, Italy [Member]
Operating Loss Carryforwards	25,000
Foreign Tax Authority [Member] | Luxembourg Inland Revenue [Member]
Operating Loss Carryforwards, Subject to Expiration	95,600
Foreign Tax Authority [Member] | Swiss Federal Tax Administration (FTA) [Member]
Operating Loss Carryforwards, Subject to Expiration	135,300
Foreign Tax Authority [Member] | Canada Revenue Agency [Member]
Operating Loss Carryforwards, Subject to Expiration	$ 1,400