Note 5 - Accounting for Stock-based Compensation (Details Textual) - USD ($)	3 Months Ended	9 Months Ended
Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross	0	0	24,000	24,000
Allocated Share-based Compensation Expense, Total	$ 5,000	$ 6,000	$ 16,000	$ 16,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period	103,500	0	322,500	50,000

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

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