Note 4 - Earnings Per Share - Shares Used in Calculation of Earnings Per Share (Details) - shares	3 Months Ended	9 Months Ended
Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Weighted-average common shares issued (in shares)	3,647,007	3,620,558	3,641,904	3,613,010
Average treasury stock shares (in shares)	(417,878)	(386,165)	(398,803)	(386,165)
Weighted-average common shares and common stock equivalents used to calculate basic earnings per share (in shares)	3,229,129	3,234,393	3,243,101	3,226,845
Additional common stock equivalents (stock options and restricted stock) used to calculate diluted earnings per share (in shares)	10,404	13,933	10,318	15,454
Weighted-average common shares and common stock equivalents used to calculate diluted earnings per share (in shares)	3,239,533	3,248,326	3,253,419	3,242,299

Additional shares included in the calculation of diluted EPS as a result of the potentially dilutive effect of share based payment arrangements using the treasury stock method.

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