Note 3 - Stock-based Compensation - Valuation Assumptions (Details) - 2004 Employee Stock Plan [Member] - Employee Stock Purchase Plan [Member]	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Expected term (Year)	6 months	6 months	6 months	6 months
Expected volatility	50.80%	63.20%	53.30%	50.60%
Risk-free interest rate	5.50%	3.10%	5.30%	1.90%
Dividend yield	0.80%	0.60%	0.80%	0.60%