Loans and Allowance for Credit Losses - Classes of loans information (Details) - USD ($)			3 Months Ended											12 Months Ended
	Jan. 20, 2023	Feb. 25, 2022	Jun. 30, 2024	Mar. 31, 2024	Dec. 31, 2023	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2022	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Sep. 30, 2021	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2022
Provision for credit losses			$ 900,000	$ 900,000	$ 900,000	$ 900,000	$ 795,000	$ 10,072,000	$ 1,138,000	$ 5,056,000	$ 240,000	$ 1,552,000	$ (305,000)	$ 3,600,000	$ 17,061,000	$ 1,487,000
Allowance for credit losses, loans														6,625,000	14,131,000	(66,000)
Provision (recovery) for off balance sheet credit exposure														(3,025,000)	2,930,000	1,553,000
Allowance for credit losses for purchased credit deteriorated (PCD)														3,600,000	$ 17,100,000	1,500,000
Impact of acquisition on provision on credit losses (PCL)														10,100,000
Impact of acquisition on allowance for credit losses (ACL)														8,900,000
Impact of acquisition on off-balance sheet credit exposure														$ 1,200,000
Net charge offs on average loans outstanding (as percentage)														5.00%	2.00%
Citizens Bancshares Company
Allowance for credit losses, loans														$ 5,200,000
Allowance for credit losses for purchased credit deteriorated (PCD)	$ 1,121,000													1,100,000
Fortune
Allowance for credit losses for purchased credit deteriorated (PCD)		$ 120,000													$ 120,000
ACL required for non-PCD loans acquired														1,900,000
Credit exposure														120,000
Negative PCL															533,000
Secured by properties located outside lending area
Loans Receivable														$ 626,300,000
Residential Real Estate
Fixed-rate and adjustable-rate mortgage (ARM) loans amortization period (in years)														30 years
Residential Real Estate | Single Family
Maximum percentage of appraised value or purchase price that loans cannot exceed														90.00%
Residential Real Estate | Multifamily
Maximum percentage of appraised value or purchase price that loans cannot exceed														85.00%
Amortization period of loans														25 years
Amortization period of multi-family residential loans if balloon maturities														10 years
Commercial real estate
Amortization period of loans														25 years
Term of fixed interest applicability on loans														10 years
Term of variable interest applicability on loans														7 years
Agricultural real estate terms if 80% loan-to-value ratio														25 years
Agricultural real estate terms if 75% loan-to-value ratio														30 years
Loans Receivable														$ 1,600,000,000
Residential Real Estate
Amortization period of loans														30 years
Allowance for credit losses, loans														$ 713,000	6,655,000	(2,238,000)
Provision (recovery) for off balance sheet credit exposure														$ 16,000	13,000	21,000
Residential Real Estate | Minimum
Maturities of single-family residential construction loans														6 months
Residential Real Estate | Maximum
Maturities of single-family residential construction loans														12 months
Commercial Real Estate
Amortization period of loans														25 years
Allowance for credit losses, loans														$ 4,100,000	5,605,000	2,251,000
Provision (recovery) for off balance sheet credit exposure														$ (105,000)	54,000	233,000
Construction Real Estate
Average term of construction loans														12 months
Allowance for credit losses, loans														$ (174,000)	432,000	46,000
Provision (recovery) for off balance sheet credit exposure														$ (2,917,000)	2,631,000	1,676,000
Construction Real Estate | Minimum
Maturities of multifamily or commercial construction loans														12 months
Construction Real Estate | Maximum
Maturities of multifamily or commercial construction loans														36 months
Consumer
Amortization period of loans														66 months
Allowance for credit losses, loans														$ 482,000	334,000	(205,000)
Provision (recovery) for off balance sheet credit exposure														$ 3,000	12,000	(157,000)
Consumer | Home Equity Loan
Maximum percentage of appraised value or purchase price that loans cannot exceed														90.00%
Amortization period of loans														10 years
Consumer | Automobile Loan
Maximum percentage of appraised value or purchase price that loans cannot exceed														100.00%
Amortization period of loans														66 months
Commercial
Amortization period of loans														5 years
Amortization period of multi-family residential loans if balloon maturities														1 year
Allowance for credit losses, loans														$ 1,504,000	1,105,000	80,000
Provision (recovery) for off balance sheet credit exposure														$ (22,000)	$ 220,000	$ (220,000)
Term Extension Modifications | Construction Real Estate
Incremental period that the loan maturity can be extended to														3 months