Note 16 - Stock Based Compensation - Stock Option Exercises (Details) - USD ($)	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Options exercised (in shares)	53,550	174,850	197,975
Net proceeds from exercise of stock options	$ 261,143	$ 670,413	$ 646,263
Intrinsic value	72,187	814,855	991,957
Tax benefit	$ 5,159	$ 12,288	$ 81,589

Amount of tax benefit for recognition of expense of award under share-based payment arrangement.

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Amount of cash inflow from exercise of option under share-based payment arrangement.

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Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares.

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

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