Note 9 - Lines of Credit and Federal Home Loan Bank Advances - Federal Home Loan Bank Advances (Details) - USD ($)		6 Months Ended	12 Months Ended
		Sep. 30, 2018	Mar. 31, 2018
Amount		$ 53,550,000	$ 60,550,000
Premium on FHLB advances assumed		1,896	122,140
Total borrowings		53,551,896	60,672,140
Borrowing One [Member] | Federal Home Loan Bank Advances [Member]
Amount	[1]	$ 5,550,000	$ 5,550,000
Rate	[1]	2.27%	1.84%
Maturity Date	[1]	Dec. 10, 2018	Jun. 11, 2018
Borrowing Two [Member] | Federal Home Loan Bank Advances [Member]
Amount	[2]	$ 6,000,000	$ 6,000,000
Rate	[2]	2.36%	1.90%
Maturity Date	[2]	Dec. 29, 2018	Jun. 29, 2018
Borrowing Three [Member] | Federal Home Loan Bank Advances [Member]
Amount		$ 1,000,000	$ 1,000,000
Rate		2.43%	2.60%
Maturity Date		Dec. 31, 2018	Jul. 02, 2018
Borrowing Four [Member] | Federal Home Loan Bank Advances [Member]
Amount		$ 3,000,000	$ 1,000,000
Rate		2.33%	3.05%
Maturity Date		Aug. 26, 2019	Jul. 03, 2018
Borrowing Five [Member] | Federal Home Loan Bank Advances [Member]
Amount		$ 3,000,000	$ 5,000,000
Rate		1.59%	3.94%
Maturity Date		Aug. 26, 2019	Jul. 23, 2018
Borrowing Six [Member] | Federal Home Loan Bank Advances [Member]
Amount		$ 1,500,000	$ 1,000,000
Rate		1.95%	1.74%
Maturity Date		Nov. 25, 2019	Jul. 31, 2018
Borrowing Seven [Member] | Federal Home Loan Bank Advances [Member]
Amount		$ 1,500,000	$ 1,000,000
Rate		1.78%	1.40%
Maturity Date		Nov. 27, 2019	Aug. 21, 2018
Borrowing Eight [Member] | Federal Home Loan Bank Advances [Member]
Amount		$ 3,000,000	$ 4,000,000
Rate		2.31%	1.94%
Maturity Date		Feb. 03, 2020	Aug. 27, 2018
Borrowing Nine [Member] | Federal Home Loan Bank Advances [Member]
Amount		$ 1,000,000	$ 3,000,000
Rate		2.86%	1.41%
Maturity Date		Aug. 04, 2020	Aug. 27, 2018
Borrowing Ten [Member] | Federal Home Loan Bank Advances [Member]
Amount		$ 2,000,000	$ 5,000,000
Rate		2.56%	3.38%
Maturity Date		Aug. 27, 2020	Sep. 19, 2018
Borrowing Eleven [Member] | Federal Home Loan Bank Advances [Member]
Amount		$ 1,000,000	$ 1,000,000
Rate		2.15%	2.60%
Maturity Date		Nov. 30, 2020	Oct. 02, 2018
Borrowing Twelve [Member] | Federal Home Loan Bank Advances [Member]
Amount		$ 2,000,000	$ 1,000,000
Rate		2.28%	1.95%
Maturity Date		Dec. 28, 2020	Dec. 31, 2018
Borrowing Thirteen [Member] | Federal Home Loan Bank Advances [Member]
Amount		$ 2,000,000	$ 3,000,000
Rate		2.49%	1.38%
Maturity Date		Feb. 01, 2021	Jul. 31, 2019
Borrowing Fourteen [Member] | Federal Home Loan Bank Advances [Member]
Amount		$ 3,000,000	$ 3,000,000
Rate		2.93%	1.96%
Maturity Date		Jul. 26, 2021	Aug. 26, 2019
Borrowing Fifteen [Member] | Federal Home Loan Bank Advances [Member]
Amount		$ 2,000,000	$ 3,000,000
Rate		3.01%	1.59%
Maturity Date		Aug. 04, 2021	Aug. 26, 2019
Borrowing Sixteen [Member] | Federal Home Loan Bank Advances [Member]
Amount		$ 1,000,000	$ 3,000,000
Rate		2.88%	1.42%
Maturity Date		Aug. 23, 2021	Aug. 26, 2019
Borrowing Seventeen [Member] | Federal Home Loan Bank Advances [Member]
Amount		$ 3,000,000	$ 1,500,000
Rate		1.48%	1.95%
Maturity Date		Aug. 25, 2021	Nov. 25, 2019
Borrowing Eighteen [Member] | Federal Home Loan Bank Advances [Member]
Amount		$ 2,000,000	$ 1,500,000
Rate		2.68%	1.78%
Maturity Date		Aug. 27, 2021	Nov. 27, 2019
Borrowing Nineteen [Member] | Federal Home Loan Bank Advances [Member]
Amount		$ 3,000,000	$ 3,000,000
Rate		2.79%	2.31%
Maturity Date		Aug. 29, 2022	Feb. 03, 2020
Borrowing Twenty [Member] | Federal Home Loan Bank Advances [Member]
Amount		$ 2,000,000	$ 1,000,000
Rate		3.14%	2.15%
Maturity Date		Sep. 19, 2022	Nov. 30, 2020
Borrowing Twenty One [Member] | Federal Home Loan Bank Advances [Member]
Amount		$ 3,000,000	$ 2,000,000
Rate		2.70%	2.28%
Maturity Date		Aug. 28, 2023	Dec. 28, 2020
Borrowing Twenty Two [Member] | Federal Home Loan Bank Advances [Member]
Amount		$ 2,000,000	$ 2,000,000
Rate		3.20%	2.49%
Maturity Date		Sep. 19, 2023	Feb. 01, 2021
Borrowing Twenty Three [Member] | Federal Home Loan Bank Advances [Member]
Amount			$ 3,000,000
Rate			1.48%
Maturity Date			Aug. 25, 2021

[1] FHLB Advance is tied to three derivative cash flow hedges in increments of $1.85 million each. The three individual cash flow hedges are for a term of five, seven and ten years, respectively and are tied to the 3-month LIBOR rate. In order for the cash flow hedges to remain effective, the corresponding FHLB Advance will have to be renewed every three months until the respective cash flow hedge matures.

[2] FHLB Advance is tied to three derivative cash flow hedges in increments of $2.0 million each. The three individual cash flow hedges are for a term of five, seven and ten years, respectively and are tied to the 3-month LIBOR rate. In order for the cash flow hedges to remain effective, the corresponding FHLB Advance will have to be renewed every three months until the respective cash flow hedge matures.