Note 5 - Loans Receivable and Allowance for Loan Losses - Summary of Troubled Debt Restructurings (Details)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)
Number of contracts	19	18
Troubled debt restructurings	$ 3,348,812	$ 3,344,039
Performing Financial Instruments [Member]
Troubled debt restructurings	1,847,156	1,835,654
Nonperforming Financial Instruments [Member]
Troubled debt restructurings	$ 1,501,656	$ 1,508,385
Real Estate Loans [Member] | Residential [Member]
Number of contracts	16	15
Troubled debt restructurings	$ 1,549,210	$ 1,543,130
Real Estate Loans [Member] | Residential [Member] | Performing Financial Instruments [Member]
Troubled debt restructurings	1,242,975	1,230,166
Real Estate Loans [Member] | Residential [Member] | Nonperforming Financial Instruments [Member]
Troubled debt restructurings	$ 306,235	$ 312,964
Real Estate Loans [Member] | Investor Loans [Member]
Number of contracts	0	0
Troubled debt restructurings	$ 0	$ 0
Real Estate Loans [Member] | Investor Loans [Member] | Performing Financial Instruments [Member]
Troubled debt restructurings	0	0
Real Estate Loans [Member] | Investor Loans [Member] | Nonperforming Financial Instruments [Member]
Troubled debt restructurings	$ 0	$ 0
Real Estate Loans [Member] | Commercial [Member]
Number of contracts	2	2
Troubled debt restructurings	$ 1,195,421	$ 1,195,421
Real Estate Loans [Member] | Commercial [Member] | Performing Financial Instruments [Member]
Troubled debt restructurings	0	0
Real Estate Loans [Member] | Commercial [Member] | Nonperforming Financial Instruments [Member]
Troubled debt restructurings	$ 1,195,421	$ 1,195,421
Real Estate Loans [Member] | Commercial Construction [Member]
Number of contracts	0	0
Troubled debt restructurings	$ 0	$ 0
Real Estate Loans [Member] | Commercial Construction [Member] | Performing Financial Instruments [Member]
Troubled debt restructurings	0	0
Real Estate Loans [Member] | Commercial Construction [Member] | Nonperforming Financial Instruments [Member]
Troubled debt restructurings	$ 0	$ 0
Commercial Portfolio Segment [Member]
Number of contracts	1	1
Troubled debt restructurings	$ 604,181	$ 605,488
Commercial Portfolio Segment [Member] | Performing Financial Instruments [Member]
Troubled debt restructurings	604,181	605,488
Commercial Portfolio Segment [Member] | Nonperforming Financial Instruments [Member]
Troubled debt restructurings	$ 0	$ 0
Home Equity Loans [Member]
Number of contracts	0	0
Troubled debt restructurings	$ 0	$ 0
Home Equity Loans [Member] | Performing Financial Instruments [Member]
Troubled debt restructurings	0	0
Home Equity Loans [Member] | Nonperforming Financial Instruments [Member]
Troubled debt restructurings	$ 0	$ 0
Consumer Portfolio Segment [Member]
Number of contracts	0	0
Troubled debt restructurings	$ 0	$ 0
Consumer Portfolio Segment [Member] | Performing Financial Instruments [Member]
Troubled debt restructurings	0	0
Consumer Portfolio Segment [Member] | Nonperforming Financial Instruments [Member]
Troubled debt restructurings	$ 0	$ 0