Note 9 - Stock-based Employee Compensation - Stock Options Valuation Assumptions (Details)	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Weighted average expected volatility	106.00%	105.00%
Weighted average expected term (Year)	6 years 10 months 24 days	6 years 7 months 6 days
Weighted average risk-free interest rate	1.70%	0.48%