Note 12 - Share Option and Equity Incentive Plans - Valuation Assumptions, Stock Options (Details) - $ / shares	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018
Expected dividend yield (%)	0.00%
Weighted-average exercise price ($) (in dollars per share)	$ 15.83
Share-based Payment Arrangement, Option [Member]
Expected dividend yield (%)
Expected volatility (%)	43.82%	43.70%
Risk-free interest rate (%)	2.19%	2.70%
Expected life of option (Year)	6 years 91 days	6 years 91 days
Weighted-average share price ($) (in dollars per share)	$ 15.83	$ 13.37
Weighted-average exercise price ($) (in dollars per share)	$ 15.83	$ 13.37

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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- Definition

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.

+ References

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- Definition

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

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- Definition

Per share weighted-average price paid for shares purchased on open market for issuance under share-based payment arrangement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901

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-Publisher FASB
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-Topic 718
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5047-113901

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- Definition

Weighted average per share amount at which grantees can acquire shares of common stock by exercise of options.

+ References

No definition available.

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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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-URI http://asc.fasb.org/extlink&oid=115993241&loc=d3e301413-122809

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