Loans - Credit quality indicators (Details) - USD ($)	Sep. 30, 2023	Jun. 30, 2023	Sep. 30, 2022
Term Loans Amortized Cost Basis by Origination Year
Total	$ 475,639,000		$ 475,639,000
Total Loans		$ 480,856,000
Residential and Consumer Loan
Term Loans Amortized Cost Basis by Origination Year
Total Loans		178,843,000
Residential and Consumer Loan | Performing
Term Loans Amortized Cost Basis by Origination Year
Total Loans		176,671,000
Residential and Consumer Loan | Nonperforming
Term Loans Amortized Cost Basis by Origination Year
Total Loans		2,172,000
Commercial Loan Total
Term Loans Amortized Cost Basis by Origination Year
Total Loans		302,013,000
Commercial Loan Total | Pass
Term Loans Amortized Cost Basis by Origination Year
Total Loans		298,921,000
Commercial Loan Total | Special Mention
Term Loans Amortized Cost Basis by Origination Year
Total Loans		1,231,000
Commercial Loan Total | Substandard
Term Loans Amortized Cost Basis by Origination Year
Total Loans		1,861,000
Residential real estate | 1-4 Family
Term Loans Amortized Cost Basis by Origination Year
2024	3,550,000
2023	8,007,000
2022	13,872,000
2021	15,786,000
2020	8,758,000
Prior	81,332,000
Total	131,305,000		131,305,000
Total Loans		135,046,000
Residential real estate | 1-4 Family | Performing
Term Loans Amortized Cost Basis by Origination Year
2024	3,550,000
2023	8,007,000
2022	13,872,000
2021	15,786,000
2020	8,627,000
Prior	79,430,000
Total	129,272,000
Total Loans		132,956,000
Residential real estate | 1-4 Family | Nonperforming
Term Loans Amortized Cost Basis by Origination Year
2020	131,000
Prior	1,902,000
Total	2,033,000
Total Loans		2,090,000
Residential real estate | Home equity and HELOCs
Term Loans Amortized Cost Basis by Origination Year
2024	535,000
2023	2,422,000
2022	517,000
2021	988,000
2020	427,000
Prior	4,677,000
Revolving Loans Amortized Cost Basis	21,156,000
Revolving Loans Converted to Term	1,775,000
Total	32,497,000		32,497,000
Total Loans		32,684,000
Residential real estate | Home equity and HELOCs | Performing
Term Loans Amortized Cost Basis by Origination Year
2024	535,000
2023	2,422,000
2022	517,000
2021	988,000
2020	427,000
Prior	4,677,000
Revolving Loans Amortized Cost Basis	21,156,000
Revolving Loans Converted to Term	1,775,000
Total	32,497,000
Total Loans		32,684,000
Residential real estate | Construction Residential
Term Loans Amortized Cost Basis by Origination Year
2024	1,728,000
2023	4,885,000
2022	645,000
2021	1,555,000
Total	8,813,000		8,813,000
Total Loans		9,113,000
Residential real estate | Construction Residential | Performing
Term Loans Amortized Cost Basis by Origination Year
2024	1,728,000
2023	4,885,000
2022	645,000
2021	1,555,000
Total	8,813,000
Total Loans		9,113,000
Commercial real estate
Term Loans Amortized Cost Basis by Origination Year
Total	53,200,000
Commercial real estate | 1-4 Family
Term Loans Amortized Cost Basis by Origination Year
Total			96,337,000
Commercial real estate | 1 - 4 family investor
Term Loans Amortized Cost Basis by Origination Year
2024	1,448,000
2023	12,185,000
2022	6,831,000
2021	17,783,000
2020	12,245,000
Prior	43,589,000
Revolving Loans Amortized Cost Basis	1,537,000
Revolving Loans Converted to Term	719,000
Total	96,337,000
Total Loans		98,160,000
Commercial real estate | 1 - 4 family investor | Pass
Term Loans Amortized Cost Basis by Origination Year
2024	1,448,000
2023	12,185,000
2022	6,831,000
2021	17,783,000
2020	12,245,000
Prior	42,376,000
Revolving Loans Amortized Cost Basis	1,537,000
Revolving Loans Converted to Term	719,000
Total	95,124,000
Total Loans		96,097,000
Commercial real estate | 1 - 4 family investor | Special Mention
Term Loans Amortized Cost Basis by Origination Year
Prior	1,102,000
Total	1,102,000
Total Loans		1,231,000
Commercial real estate | 1 - 4 family investor | Substandard
Term Loans Amortized Cost Basis by Origination Year
2024	0
2023	0
2022	0
2021	0
2020	0
Prior	111,000
Revolving Loans Amortized Cost Basis	0
Revolving Loans Converted to Term	0
Total	111,000
Total Loans		832,000
Commercial real estate | Multi-family (five or more)
Term Loans Amortized Cost Basis by Origination Year
2024	101,000
2023	1,181,000
2022	1,346,000
2021	4,173,000
2020	5,050,000
Prior	3,407,000
Total	15,258,000		15,258,000
Total Loans		15,281,000
Commercial real estate | Multi-family (five or more) | Pass
Term Loans Amortized Cost Basis by Origination Year
2024	101,000
2023	1,181,000
2022	1,346,000
2021	4,173,000
2020	5,050,000
Prior	3,171,000
Total	15,022,000
Total Loans		15,030,000
Commercial real estate | Multi-family (five or more) | Substandard
Term Loans Amortized Cost Basis by Origination Year
Prior	236,000
Total	236,000
Total Loans		251,000
Commercial real estate | Commercial non-residential
Term Loans Amortized Cost Basis by Origination Year
2024	553,000
2023	21,986,000
2022	62,611,000
2021	30,998,000
2020	16,967,000
Prior	22,188,000
Revolving Loans Converted to Term	96,000
Total	155,399,000		155,399,000
Total Loans		157,555,000
Commercial real estate | Commercial non-residential | Pass
Term Loans Amortized Cost Basis by Origination Year
2024	553,000
2023	21,986,000
2022	62,611,000
2021	30,678,000
2020	16,490,000
Prior	21,890,000
Revolving Loans Converted to Term	96,000
Total	154,304,000
Total Loans		156,777,000
Commercial real estate | Commercial non-residential | Substandard
Term Loans Amortized Cost Basis by Origination Year
2021	320,000
2020	477,000
Prior	298,000
Total	1,095,000
Total Loans		778,000
Commercial real estate | Construction and land
Term Loans Amortized Cost Basis by Origination Year
2024	811,000
2023	4,742,000
2022	10,501,000
2020	1,167,000
Prior	2,122,000
Total	19,343,000		19,343,000
Total Loans		15,584,000
Commercial real estate | Construction and land | Pass
Term Loans Amortized Cost Basis by Origination Year
2024	811,000
2023	4,742,000
2022	10,501,000
2020	1,167,000
Prior	2,122,000
Total	19,343,000
Total Loans		15,584,000
Commercial
Term Loans Amortized Cost Basis by Origination Year
2023	6,803,000
2022	7,378,000
2020	53,000
Prior	525,000
Total	14,759,000		14,759,000
Total Loans		15,433,000
Commercial | Pass
Term Loans Amortized Cost Basis by Origination Year
2023	6,803,000
2022	7,378,000
2020	53,000
Prior	525,000
Total	14,759,000
Total Loans		15,433,000
Consumer
Term Loans Amortized Cost Basis by Origination Year
2023	116,000
2022	68,000
2021	25,000
2020	321,000
Prior	1,398,000
Total	1,928,000		$ 1,928,000
Total Loans		2,000,000
Consumer | Performing
Term Loans Amortized Cost Basis by Origination Year
2023	116,000
2022	68,000
2021	25,000
2020	321,000
Prior	1,317,000
Total	1,847,000
Total Loans		1,918,000
Consumer | Nonperforming
Term Loans Amortized Cost Basis by Origination Year
Prior	81,000
Total	$ 81,000
Total Loans		$ 82,000