Note 7 - Stock-based Compensation - Valuation Assumptions (Details) - 2004 Employee Stock Plan [Member] - Employee Stock Purchase Plan [Member]	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Expected term (Year)	6 months	6 months	6 months
Expected volatility	53.30%	50.60%	43.20%
Risk-free interest rate	5.30%	1.90%	0.10%
Dividend yield	0.80%	0.60%	0.60%