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Loans and Allowance for Credit Losses - Summary of Impaired Loans (Detail) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Sep. 30, 2021	Jun. 30, 2022
Financing Receivable, Impaired [Line Items]
Recorded Balance	$ 1,129	$ 1,385
Unpaid Principal Balance	1,129	1,385
Specific Allowance	0	0
Average Investment in Impaired Loans	1,132	1,401
Interest Income Recognized	6	19
Interest on Cash Basis	5	17
Commercial [Member]
Financing Receivable, Impaired [Line Items]
Recorded Balance, Loans without a specific valuation allowance	43	35
Unpaid Principal Balance, Loans without a specific valuation allowance	43	35
Average Investment in Impaired Loans, Loans without a specific valuation allowance	44	40
Interest Income Recognized, Loans without a specific valuation allowance	1	4
Interest on Cash Basis, Loans without a specific valuation allowance	1	4
Recorded Balance	43	35
Unpaid Principal Balance	43	35
Average Investment in Impaired Loans	44	40
Interest Income Recognized	1	4
Interest on Cash Basis	1	4
One- to four-family [Member]
Financing Receivable, Impaired [Line Items]
Recorded Balance, Loans without a specific valuation allowance	1,086	1,350
Unpaid Principal Balance, Loans without a specific valuation allowance	1,086	1,350
Average Investment in Impaired Loans, Loans without a specific valuation allowance	1,088	1,361
Interest Income Recognized, Loans without a specific valuation allowance	5	15
Interest on Cash Basis, Loans without a specific valuation allowance	4	13
Recorded Balance	1,086	1,350
Unpaid Principal Balance	1,086	1,350
Average Investment in Impaired Loans	1,088	1,361
Interest Income Recognized	5	15
Interest on Cash Basis	$ 4	$ 13

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