Note 5 - Loans Receivable and Allowance for Loan Losses - Outstanding Commitments and Unused Lines of Credit (Details) - USD ($)	Jun. 30, 2018	Mar. 31, 2018
Unused Commercial Lines of Credit [Member]
Outstanding commitments and unused lines of credit	$ 11,325,807	$ 9,187,810
Unused Home Equity Lines of Credit [Member]
Outstanding commitments and unused lines of credit	24,296,445	22,560,376
Unused Consumer Lines of Credit [Member]
Outstanding commitments and unused lines of credit	185,417	29,331
Residential Construction Loan Commitments [Member]
Outstanding commitments and unused lines of credit	5,600,272	4,234,076
Commercial Construction Loan Commitments [Member]
Outstanding commitments and unused lines of credit	8,147,129	8,968,416
Home Equity Loan Commitments [Member]
Outstanding commitments and unused lines of credit	696,000	389,600
Commercial loan commitments [Member]
Outstanding commitments and unused lines of credit	4,490,151	5,125,000
Standby Letters of Credit [Member]
Outstanding commitments and unused lines of credit	$ 415,607	$ 250,224