Note 11 - Income Taxes (Details Textual) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount	$ 9,800
Unrecognized Tax Benefits, Ending Balance	1,620	$ 1,512	$ 1,363
Unrecognized Tax Benefits, Income Tax Penalties and Interest Accrued, Total	$ 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, Total	$ 364,300
Operating Loss Carryforwards, Subject to Expiration	254,500
Operating Loss Carryforwards, Not Subject to Expiration	109,800
Domestic Tax Authority [Member] | Research Tax Credit Carryforward [Member]
Tax Credit Carryforward, Amount	7,200
State and Local Jurisdiction [Member]
Operating Loss Carryforwards, Total	296,200
Operating Loss Carryforwards, Subject to Expiration	289,300
Operating Loss Carryforwards, Not Subject to Expiration	6,800
Foreign Tax Authority [Member] | Ministry of Economic Affairs and Finance, Italy [Member]
Operating Loss Carryforwards, Total	24,500
Foreign Tax Authority [Member] | Luxembourg Inland Revenue [Member]
Operating Loss Carryforwards, Subject to Expiration	95,100
Foreign Tax Authority [Member] | Swiss Federal Tax Administration (FTA) [Member]
Operating Loss Carryforwards, Subject to Expiration	$ 61,900