Note 14 - Equity Incentive Plan - Assumptions Used to Estimate Fair Value of Stock Options and Stock Appreciation Rights (Details)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Expected life of options (in years) (Year)			3 years 6 months
Expected dividend yield	0.00%	0.00%	0.00%
Fair value per option	0.1480	0.1631	0.1473
Expected life of options (in years) (Year)			3 years 6 months
Expected dividend yield	0.00%	0.00%	0.00%
Employee Stock Purchase Plan (ESPP) [Member]
Risk-free interest rate	0.06%
Expected stock price volatility	32.58%
Expected life of options (in years) (Year)	6 months
Expected dividend yield	0.00%
Risk-free interest rate	0.06%
Expected stock price volatility	32.58%
Expected life of options (in years) (Year)	6 months
Expected dividend yield	0.00%
Minimum [Member]
Risk-free interest rate	0.29%	0.21%	1.41%
Expected stock price volatility	54.80%	46.48%	44.27%
Risk-free interest rate	0.29%	0.21%	1.41%
Expected stock price volatility	54.80%	46.48%	44.27%
Maximum [Member]
Risk-free interest rate	1.00%	1.59%	2.54%
Expected stock price volatility	56.35%	54.06%	48.52%
Risk-free interest rate	1.00%	1.59%	2.54%
Expected stock price volatility	56.35%	54.06%	48.52%