Note 13 - Income Taxes (Details Textual) - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance, Amount	$ 47,954,000	$ 38,551,000	$ 23,824,000
Unrecognized Tax Benefits, Income Tax Penalties and Interest Accrued, Total	0	0	0
Undistributed Earnings of Foreign Subsidiaries	$ 750,000
Open Tax Year	2018 2019 2020 2021
Research Tax Credit Carryforward [Member]
Tax Credit Carryforward, Amount	$ 80,925
Domestic Tax Authority [Member]
Operating Loss Carryforwards, Total	$ 480,331,000
State and Local Jurisdiction [Member]
Operating Loss Carryforwards, Total		$ 177,567,000
Foreign Tax Authority [Member]
Operating Loss Carryforwards, Total			$ 29,355,000