Note 6 - Loans Receivable and Allowance for Loan Losses - Summary of Troubled Debt Restructurings (Details)	Sep. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)
Number of contracts	17	16
Troubled debt restructurings	$ 3,686,379	$ 3,747,382
Performing Financial Instruments [Member]
Troubled debt restructurings	1,854,810	1,905,602
Nonperforming Financial Instruments [Member]
Troubled debt restructurings	$ 1,831,569	$ 1,841,780
Real Estate Loans [Member] | Residential [Member]
Number of contracts	14	13
Troubled debt restructurings	$ 1,530,798	$ 1,556,571
Real Estate Loans [Member] | Residential [Member] | Performing Financial Instruments [Member]
Troubled debt restructurings	1,246,041	1,261,603
Real Estate Loans [Member] | Residential [Member] | Nonperforming Financial Instruments [Member]
Troubled debt restructurings	$ 284,757	$ 294,968
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	$ 1,546,812	$ 1,546,812
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	$ 1,546,812	$ 1,546,812
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	$ 608,769	$ 643,999
Commercial Portfolio Segment [Member] | Performing Financial Instruments [Member]
Troubled debt restructurings	608,769	643,999
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
Troubled debt restructurings		$ 0
Consumer Portfolio Segment [Member] | Performing Financial Instruments [Member]
Troubled debt restructurings		0
Consumer Portfolio Segment [Member] | Nonperforming Financial Instruments [Member]
Troubled debt restructurings	$ 0	$ 0