Note 8 - EMPLOYEE BENEFIT PLANS - Stock Options, Valuation Assumptions (Details) - $ / shares	3 Months Ended	9 Months Ended
Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Employee Stock Purchase Plan [Member]
Expected life (in years) (Year)	1 year 3 months		1 year 3 months	1 year 3 months
Volatility	48.00%		34.25%	34.25%
Risk-free interest rate	0.11%		1.43%	1.43%
Expected dividend	0.00%		0.00%	0.00%
Weighted average fair value of purchase rights granted during the period (in dollars per share)	$ 6.71		$ 4.83	$ 4.83
Twenty Eleven Stock Incentive Plan [Member]
Expected life (in years) (Year)		4 years 5 months 12 days		4 years 5 months 12 days
Volatility		43.92%		40.90%
Risk-free interest rate		0.23%		0.60%
Expected dividend		0.00%		0.00%
Weighted average fair value of purchase rights granted during the period (in dollars per share)		$ 6.92		$ 5.75

The estimated dividend rate (a percentage of the share price) to be paid (expected dividends) to holders of the underlying shares over the option's term.

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The estimated measure of the percentage by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probability-weighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period.

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The risk-free interest rate assumption that is used in valuing an option on its own shares.

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- Definition

The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology.

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- Definition

Expected term of award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
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-Paragraph 2
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-Name Accounting Standards Codification
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