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, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Expected term (Year)	6 months	6 months	6 months	6 months
Expected volatility	63.20%	43.00%	50.60%	43.20%
Risk-free interest rate	3.10%	0.10%	1.90%	0.10%
Dividend yield	0.60%	0.50%	0.60%	0.60%