Note 7 - Derivative - Interest Rate Swap Agreement - Cash Flow Derivative Gains (Loss) Recorded In AOCI and the Statement of Income (Details) - USD ($)	3 Months Ended	6 Months Ended
Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Unrealized gain on derivative transactions, net of tax effect			$ 193,845	$ (27,326)
Interest Rate Swap [Member] \| Cash Flow Hedging [Member]
Unrealized gain on derivative transactions, net of tax effect	$ 95,806	$ 26,710	193,845	(183,238)
Interest Rate ContraAmount of gain (loss) reclassified from OCI to Interest Incomet
Amount of gain (loss) recognized in Other Noninterest Income (ineffective portion)	$ 540	$ (3,679)	$ 921	$ (3,679)

The effective portion of net gain (loss) reclassified from accumulated other comprehensive income into income on derivative instruments designated and qualifying as hedging instruments.

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The portion of gains and losses (net) on derivative instruments designated and qualifying as hedging instruments representing (a) the amount of the hedge ineffectiveness and (b) the amount, if any, excluded from the assessment of hedge effectiveness.

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Amount after tax of increase (decrease) in accumulated gain (loss) from derivative instruments designated and qualifying as the effective portion of cash flow hedges and an entity's share of an equity investee's increase (decrease) in deferred hedging gain (loss).

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