Note 6 - Equity Incentive Plan - Granted and Exercised Stock-based Compensation Awards (Details) - shares	3 Months Ended	9 Months Ended
Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Employee Stock Option [Member]
Stock options (in shares)	18,500	60,609	228,300	470,744
Stock options (in shares)		3,329	284,548	12,766
Restricted Stock [Member]
Restricted stock grants (in shares)		14,506	64,578	14,506
Restricted Stock Units (RSUs) [Member]
Restricted stock grants (in shares)	3,624		11,754	9,970
Stock Appreciation Rights (SARs) [Member]
SARs (in shares)				5,000

The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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Number of non-option equity instruments exercised by participants.

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Gross number of share options (or share units) granted during the period.

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Number of share options (or share units) exercised during the current period.

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