Note 5 - Stock-based Compensation (Details Textual) - USD ($)	12 Months Ended
Mar. 31, 2019	Mar. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period	5 years
Allocated Share-based Compensation Expense, Total	$ 93,360	$ 40,920
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Dividend Rate	3.70%	5.30%
Employee Service Share-based Compensation, Tax Benefit from Exercise of Stock Options	$ 19,771	$ 8,953
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Remaining Contractual Term	6 years 255 days	6 years 219 days
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Intrinsic Value	$ 180,093
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value	633,840
Share-based Compensation Arrangement by Share Based Payment Award Options Grants in Period Fair Value	93,360
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Total	$ 0
Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period	1 year
Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period	10 years

Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Fair Value

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Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

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Unrecognized cost of unvested share-based compensation awards.

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Amount of tax benefit from exercise of stock options granted under share-based compensation arrangement.

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Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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The estimated dividend rate (a percentage of the share price) to be paid (expected dividends) to holders of the underlying shares over the option's term.

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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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Amount by which the current fair value of the underlying stock exceeds the exercise price of options outstanding.

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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.

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Weighted average remaining contractual term for vested portions of options outstanding and currently exercisable or convertible, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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