Loans and Allowance for Credit Losses - Classes of loans information (Details) $ in Thousands		3 Months Ended		9 Months Ended
	Jan. 20, 2023 USD ($)	Mar. 31, 2023 USD ($)	Mar. 31, 2022 USD ($)	Mar. 31, 2023 USD ($)	Mar. 31, 2022 USD ($)	Dec. 31, 2022 USD ($)	Jun. 30, 2022 USD ($)	Dec. 31, 2021 USD ($)	Jun. 30, 2021 USD ($)
Allowance for credit losses		$ 10,100	$ 1,600	$ 16,300	$ 1,200
Off-balance sheet credit exposures		7,824	2,679	7,824	$ 2,679	$ 4,937	$ 3,358	$ 2,179	$ 1,805
Impact of acquisition on provision on credit losses (PCL)		3,100		9,300
Impact of acquisition on allowance for credit losses (ACL)		2,000		6,600
Impact of acquisition on off-balance sheet credit exposure		1,100		$ 2,700
Net charge offs on average loans outstanding (as percentage)				0.02%	0.01%
Citizens Bancshares Company, purchased on January 20, 2023
Allowance for credit losses	$ 5,200
Allowance for credit losses for purchased credit deteriorated (PCD)	1,100
Off-balance sheet credit exposures	$ 1,800
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
Amortization period of loans				25 years
Amortization period of multi-family residential loans if balloon maturities				10 years
Commercial
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
Residential Real Estate
Amortization period of loans				30 years
Off-balance sheet credit exposures		105	83	$ 105	$ 83	70	58	34	37
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
Off-balance sheet credit exposures		341	335	$ 341	335	480	421	170	188
Construction Real Estate
Average term of construction loans				12 months
Off-balance sheet credit exposures		5,578	1,723	$ 5,578	1,723	3,629	2,178	1,673	502
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 loans
Amortization period of loans				66 months
Off-balance sheet credit exposures		102	74	$ 102	74	56	61	58	218
Consumer loans | Home Equity Loan
Maximum percentage of appraised value or purchase price that loans cannot exceed				100.00%
Amortization period of loans				10 years
Consumer loans | Automobile loans
Maximum percentage of appraised value or purchase price that loans cannot exceed				100.00%
Amortization period of loans				66 months
Commercial loans
Amortization period of loans				5 years
Amortization period of multi-family residential loans if balloon maturities				1 year
Off-balance sheet credit exposures		$ 1,698	$ 464	$ 1,698	$ 464	$ 702	$ 640	$ 244	$ 860
Modifications for the purpose of extending the maturity date | Construction Real Estate
Incremental period that the loan maturity can be extended to				3 months
Number of construction loans outstanding, for which a modification had been agreed to		79		79			57
Construction loans outstanding, for which a modification had been agreed to		$ 68,500		$ 68,500			$ 13,800