Note 9 - Stock-based Compensation (Details Textual) - shares		12 Months Ended
Aug. 23, 2017	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross	60,000
Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period		5 years
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested, Number of Shares	60,000

Period from grant date that an equity-based award expires, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)(2)
-URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901

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