Note 12 - Common Stock Options (Details Textual) - shares	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2004	Dec. 31, 2000	Dec. 31, 1997
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized						450,000
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Term	91 days	91 days	91 days			10 years
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period						1 year
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross	0	0	0	40,049	54,000	450,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period	0	0	0

Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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- Definition

The maximum number of shares (or other type of equity) originally approved (usually by shareholders and board of directors), net of any subsequent amendments and adjustments, for awards under the equity-based compensation plan. As stock or unit options and equity instruments other than options are awarded to participants, the shares or units remain authorized and become reserved for issuance under outstanding awards (not necessarily vested).

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- Definition

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

+ References

No definition available.

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- Definition

Expected term of share-based compensation awards, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
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-Subparagraph (f)(2)(i)
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Number of share options (or share units) exercised during the current period.

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