Note 4 - Accounting for Stock-based Compensation (Details Textual) - USD ($)	3 Months Ended	9 Months Ended
Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross	0	0	24,000	24,000
Share-based Payment Arrangement, Expense	$ 10,000	$ 5,000	$ 24,000	$ 16,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period	10,500	103,500	291,000	322,500

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

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
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-Name Accounting Standards Codification
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Period Type:	duration