Loans - Allowance for loan losses (Details) - USD ($)	3 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Jun. 30, 2023
Allowance for credit losses:
Beginning balance	$ 3,313,000	$ 3,409,000
Charge-offs		(79,000)
Recoveries	26,000
Recoveries		3,000
Provision (recovery)	5,000
Ending balance	3,587,000	3,587,000
Ending Balance		3,333,000
Allowance ending balance:
Collectively evaluated for impairment		3,587,000
Collectively evaluated for impairment			$ 3,313,000
Allowance for loan losses	3,587,000	3,587,000
Allowance for loan losses		3,333,000	3,313,000
Loans receivable ,Individually evaluated for impairment		3,556,000	3,252,000
Loans receivable, Collectively evaluated for impairment		472,083,000	380,012,000
Total Loans	475,639,000	475,639,000
Total Loans			480,856,000
Cumulative Effect, Period of Adoption, Adjustment
Allowance for credit losses:
Beginning balance	243,000
Allowance ending balance:
Allowance for loan losses			243,000
Acquired credit impaired
Allowance ending balance:
Loans receivable, Collectively evaluated for impairment			72,000
Acquired non-credit impaired
Allowance ending balance:
Loans receivable, Collectively evaluated for impairment			97,520,000
Residential real estate | 1-4 Family
Allowance for credit losses:
Beginning balance	486,000	506,000
Beginning balance	419,000
Charge-offs		(79,000)
Provision (recovery)	(12,000)
Provision (recovery)		66,000
Ending balance	407,000	407,000
Ending Balance		493,000
Allowance ending balance:
Collectively evaluated for impairment		407,000
Collectively evaluated for impairment			486,000
Allowance for loan losses	407,000	407,000	419,000
Allowance for loan losses		493,000	486,000
Loans receivable ,Individually evaluated for impairment		2,033,000	1,209,000
Loans receivable, Collectively evaluated for impairment		129,272,000	78,237,000
Total Loans	131,305,000	131,305,000
Total Loans			135,046,000
Residential real estate | 1-4 Family | Cumulative Effect, Period of Adoption, Adjustment
Allowance for credit losses:
Beginning balance	(67,000)
Allowance ending balance:
Allowance for loan losses			(67,000)
Residential real estate | 1-4 Family | Acquired credit impaired
Allowance ending balance:
Loans receivable, Collectively evaluated for impairment			72,000
Residential real estate | 1-4 Family | Acquired non-credit impaired
Allowance ending balance:
Loans receivable, Collectively evaluated for impairment			55,528,000
Residential real estate | Home equity and HELOCs
Allowance for credit losses:
Beginning balance	113,000	113,000
Beginning balance	132,000
Provision (recovery)	(1,000)
Provision (recovery)		3,000
Ending balance	131,000	131,000
Ending Balance		116,000
Allowance ending balance:
Collectively evaluated for impairment		131,000
Collectively evaluated for impairment			113,000
Allowance for loan losses	131,000	131,000	132,000
Allowance for loan losses		116,000	113,000
Loans receivable ,Individually evaluated for impairment			182,000
Loans receivable, Collectively evaluated for impairment		32,497,000	19,689,000
Total Loans	32,497,000	32,497,000
Total Loans			32,684,000
Residential real estate | Home equity and HELOCs | Cumulative Effect, Period of Adoption, Adjustment
Allowance for credit losses:
Beginning balance	19,000
Allowance ending balance:
Allowance for loan losses			19,000
Residential real estate | Home equity and HELOCs | Acquired non-credit impaired
Allowance ending balance:
Loans receivable, Collectively evaluated for impairment			12,813,000
Residential real estate | Construction Residential
Allowance for credit losses:
Beginning balance	214,000	386,000
Beginning balance	40,000
Provision (recovery)	(1,000)
Provision (recovery)		(85,000)
Ending balance	39,000	39,000
Ending Balance		301,000
Allowance ending balance:
Collectively evaluated for impairment		39,000
Collectively evaluated for impairment			214,000
Allowance for loan losses	39,000	39,000	40,000
Allowance for loan losses		301,000	214,000
Loans receivable, Collectively evaluated for impairment		8,813,000	9,113,000
Total Loans	8,813,000	8,813,000
Total Loans			9,113,000
Residential real estate | Construction Residential | Cumulative Effect, Period of Adoption, Adjustment
Allowance for credit losses:
Beginning balance	(174,000)
Allowance ending balance:
Allowance for loan losses			(174,000)
Commercial real estate
Allowance ending balance:
Total Loans	53,200,000
Commercial real estate | 1-4 Family
Allowance for credit losses:
Ending balance		325,000
Allowance ending balance:
Collectively evaluated for impairment		325,000
Allowance for loan losses		325,000
Loans receivable ,Individually evaluated for impairment		111,000
Loans receivable, Collectively evaluated for impairment		96,226,000
Total Loans		96,337,000
Commercial real estate | 1 - 4 family investor
Allowance for credit losses:
Beginning balance	569,000	527,000
Beginning balance	328,000
Provision (recovery)	(3,000)
Provision (recovery)		(32,000)
Ending balance	325,000
Ending Balance		495,000
Allowance ending balance:
Collectively evaluated for impairment			569,000
Allowance for loan losses	325,000		328,000
Allowance for loan losses		495,000	569,000
Loans receivable ,Individually evaluated for impairment			832,000
Loans receivable, Collectively evaluated for impairment			84,891,000
Total Loans	96,337,000
Total Loans			98,160,000
Commercial real estate | 1 - 4 family investor | Cumulative Effect, Period of Adoption, Adjustment
Allowance for credit losses:
Beginning balance	(241,000)
Allowance ending balance:
Allowance for loan losses			(241,000)
Commercial real estate | 1 - 4 family investor | Acquired non-credit impaired
Allowance ending balance:
Loans receivable, Collectively evaluated for impairment			12,437,000
Commercial real estate | Multi-family (five or more)
Allowance for credit losses:
Beginning balance	89,000	110,000
Beginning balance	59,000
Provision (recovery)	(6,000)
Provision (recovery)		2,000
Ending balance	53,000	53,000
Ending Balance		112,000
Allowance ending balance:
Collectively evaluated for impairment		53,000
Collectively evaluated for impairment			89,000
Allowance for loan losses	53,000	53,000	59,000
Allowance for loan losses		112,000	89,000
Loans receivable ,Individually evaluated for impairment		236,000	251,000
Loans receivable, Collectively evaluated for impairment		15,022,000	14,781,000
Total Loans	15,258,000	15,258,000
Total Loans			15,281,000
Commercial real estate | Multi-family (five or more) | Cumulative Effect, Period of Adoption, Adjustment
Allowance for credit losses:
Beginning balance	(30,000)
Allowance ending balance:
Allowance for loan losses			(30,000)
Commercial real estate | Multi-family (five or more) | Acquired non-credit impaired
Allowance ending balance:
Loans receivable, Collectively evaluated for impairment			249,000
Commercial real estate | Commercial non-residential
Allowance for credit losses:
Beginning balance	1,420,000	1,451,000
Beginning balance	1,799,000
Provision (recovery)	(32,000)
Provision (recovery)		(20,000)
Ending balance	1,767,000	1,767,000
Ending Balance		1,431,000
Allowance ending balance:
Collectively evaluated for impairment		1,767,000
Collectively evaluated for impairment			1,420,000
Allowance for loan losses	1,767,000	1,767,000	1,799,000
Allowance for loan losses		1,431,000	1,420,000
Loans receivable ,Individually evaluated for impairment		1,095,000	778,000
Loans receivable, Collectively evaluated for impairment		154,304,000	142,098,000
Total Loans	155,399,000	155,399,000
Total Loans			157,555,000
Commercial real estate | Commercial non-residential | Cumulative Effect, Period of Adoption, Adjustment
Allowance for credit losses:
Beginning balance	379,000
Allowance ending balance:
Allowance for loan losses			379,000
Commercial real estate | Commercial non-residential | Acquired non-credit impaired
Allowance ending balance:
Loans receivable, Collectively evaluated for impairment			14,679,000
Commercial real estate | Construction and land
Allowance for credit losses:
Beginning balance	281,000	166,000
Beginning balance	188,000
Provision (recovery)	45,000
Provision (recovery)		58,000
Ending balance	233,000	233,000
Ending Balance		224,000
Allowance ending balance:
Collectively evaluated for impairment		233,000
Collectively evaluated for impairment			281,000
Allowance for loan losses	233,000	233,000	188,000
Allowance for loan losses		224,000	281,000
Loans receivable, Collectively evaluated for impairment		19,343,000	15,584,000
Total Loans	19,343,000	19,343,000
Total Loans			15,584,000
Commercial real estate | Construction and land | Cumulative Effect, Period of Adoption, Adjustment
Allowance for credit losses:
Beginning balance	(93,000)
Allowance ending balance:
Allowance for loan losses			(93,000)
Commercial
Allowance for credit losses:
Beginning balance	82,000	100,000
Beginning balance	336,000
Provision (recovery)	4,000
Provision (recovery)		11,000
Ending balance	340,000	340,000
Ending Balance		111,000
Allowance ending balance:
Collectively evaluated for impairment		340,000
Collectively evaluated for impairment			82,000
Allowance for loan losses	340,000	340,000	336,000
Allowance for loan losses		111,000	82,000
Loans receivable, Collectively evaluated for impairment		14,759,000	14,976,000
Total Loans	14,759,000	14,759,000
Total Loans			15,433,000
Commercial | Cumulative Effect, Period of Adoption, Adjustment
Allowance for credit losses:
Beginning balance	254,000
Allowance ending balance:
Allowance for loan losses			254,000
Commercial | Acquired non-credit impaired
Allowance ending balance:
Loans receivable, Collectively evaluated for impairment			457,000
Consumer
Allowance for credit losses:
Beginning balance	59,000	50,000
Beginning balance	255,000
Recoveries	26,000
Recoveries		3,000
Provision (recovery)	11,000
Provision (recovery)		(3,000)
Ending balance	292,000	292,000
Ending Balance		50,000
Allowance ending balance:
Collectively evaluated for impairment		292,000
Collectively evaluated for impairment			59,000
Allowance for loan losses	292,000	292,000	255,000
Allowance for loan losses		50,000	59,000
Loans receivable ,Individually evaluated for impairment		81,000
Loans receivable, Collectively evaluated for impairment		1,847,000	643,000
Total Loans	1,928,000	$ 1,928,000
Total Loans			2,000,000
Consumer | Cumulative Effect, Period of Adoption, Adjustment
Allowance for credit losses:
Beginning balance	$ 196,000
Allowance ending balance:
Allowance for loan losses			196,000
Consumer | Acquired non-credit impaired
Allowance ending balance:
Loans receivable, Collectively evaluated for impairment			$ 1,357,000