Note 5 - Loans Receivable and Allowance for Loan Losses - Outstanding Commitments and Unused Lines of Credit (Details) - USD ($)	Sep. 30, 2018	Mar. 31, 2018
Unused Commercial Lines of Credit [Member]
Outstanding commitments and unused lines of credit	$ 11,536,470	$ 9,187,810
Unused Home Equity Lines of Credit [Member]
Outstanding commitments and unused lines of credit	23,299,018	22,560,376
Unused Consumer Lines of Credit [Member]
Outstanding commitments and unused lines of credit	26,845	29,331
Residential Construction Loan Commitments [Member]
Outstanding commitments and unused lines of credit	7,814,167	4,234,076
Commercial Construction Loan Commitments [Member]
Outstanding commitments and unused lines of credit	2,535,935	8,968,416
Home Equity Loan Commitments [Member]
Outstanding commitments and unused lines of credit	353,000	389,600
Commercial loan commitments [Member]
Outstanding commitments and unused lines of credit	3,359,375	5,125,000
Standby Letters of Credit [Member]
Outstanding commitments and unused lines of credit	$ 416,449	$ 250,224