Note 13 - Equity Incentive Plans - Fair Value Assumptions (Details)	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Minimum [Member]
Expected volatility	90.50%	91.50%
Risk-free interest rate	1.83%
Expected lives (years) (Year)	5 years	5 years
Maximum [Member]
Expected volatility	92.30%	92.70%
Risk-free interest rate	2.76%	0.43%
Expected lives (years) (Year)	6 years 3 months	6 years 3 months