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Loans and Allowance for Loan Losses - Additional Information (Detail) | 3 Months Ended | 6 Months Ended | 12 Months Ended |
--- | --- | --- | --- | ---
Sep. 30, 2021 USD ($) Loans SecurityLoan | Sep. 30, 2020 USD ($) | Dec. 31, 2019 | Jun. 30, 2021 USD ($) SecurityLoan | Jun. 30, 2020 USD ($)
Loans and Allowance for Credit Losses [Line Items] |  |  |  |  |
Maximum amount of one-to-four family residential mortgage loans can be approved by loan officer | $ 100,000 |  |  |  |
Maximum amount of other secured loans real estate loans can be approved by loan officer | 50,000 |  |  |  |
Maximum amount of unsecured loans real estate loans can be approved by loan officer | 10,000 |  |  |  |
Maximum amount of one-to-four family residential mortgage loans can be approved by managing officer | 375,000 |  |  |  |
Maximum amount other secured loans residential mortgage loans can be approved by managing officer | 375,000 |  |  |  |
Maximum amount of unsecured loans residential mortgage loans can be approved by managing officer | $ 100,000 |  |  |  |
Maximum amount of unsecured loans real estate loans can be approved by loan committee |  |  |  | $ 500,000 |
Maximum aggregate loan amount of one-to four-family residential mortgage loans, commercial real estate loans, multi-family real estate loans and land loans can be approved by loan committee |  |  |  | 2,000,000 |
Maximum term of fixed-rate one- to four-family residential mortgage loans | 15 years |  |  |  |
Troubled debt restructurings, Impaired loans | $ 1,095,000 |  |  |  | $ 1,264,000
Number of default loans | SecurityLoan | 0 |  |  |  |
Investment recorded prior to modification |  | $ 0 |  | 0 |
Residential real estate properties foreclosure proceedings | $ 34,000 |  |  |  |
Loans and Leases Receivable, Gross | 512,984,000 | 525,033,000 |  | 520,526,000 |
Fair Value, Concentration of Risk, Collateral Policy [Member] |  |  |  |  |
Loans and Allowance for Credit Losses [Line Items] |  |  |  |  |
Commercial and multi-family real estate | 280,257,000 |  |  | 274,892,000 |
Troubled Debt Restructurings [Member] |  |  |  |  |
Loans and Allowance for Credit Losses [Line Items] |  |  |  |  |
Troubled debt restructurings, Impaired loans | $ 1,100,000 |  |  |  |
Minimum period for default | 90 days |  |  |  |
Commercial Business Loans [Member] |  |  |  |  |
Loans and Allowance for Credit Losses [Line Items] |  |  |  |  |
Troubled debt restructurings, Impaired loans | $ 43,000 |  |  |  | 46,000
Loans and Leases Receivable, Gross | $ 88,962,000 | 109,182,000 |  | 103,088,000 |
Commercial Business Loans [Member] | Small Business Administration Paycheck Protection Programme Loans [Member] |  |  |  |  |
Loans and Allowance for Credit Losses [Line Items] |  |  |  |  |
Percentage of government guarantee for loans as per scheme | 100.00% |  |  |  |
Commercial Portfolio And Commercial Residential Portfolio [Member] |  |  |  |  |
Loans and Allowance for Credit Losses [Line Items] |  |  |  |  |
Number of loans as on closing date | Loans | 165 |  |  |  |
Loans and Leases Receivable, Gross | $ 14.3 |  |  |  |
One- to four-family [Member] |  |  |  |  |
Loans and Allowance for Credit Losses [Line Items] |  |  |  |  |
Loans held for sale | $ 216,000 |  |  | 632,000 |
Maximum term of fixed-rate one- to four-family residential mortgage loans | 15 years |  |  |  |
Troubled debt restructurings, Impaired loans | $ 1,052,000 |  |  |  | $ 1,218,000
Investment recorded post modification | 118,000 |  |  |  |
Loans and Leases Receivable, Gross | 117,854,000 | $ 125,574,000 |  | $ 117,435,000 |
One- to four-family [Member] | Troubled Debt Restructurings [Member] |  |  |  |  |
Loans and Allowance for Credit Losses [Line Items] |  |  |  |  |
Number of default loans | SecurityLoan |  |  |  | 1 |
Investment recorded post modification | 118,000 |  |  |  |
Purchased Loans and Loan Participations [Member] |  |  |  |  |
Loans and Allowance for Credit Losses [Line Items] |  |  |  |  |
Approximate amount of purchase loans included in loans receivable | 1,648,000 |  |  | $ 3,578,000 |
Approximate amount of loans included on out-of-area participation | 25,577,000 |  |  | 26,870,000 |
Amount within 100 miles of primary area | 8,542,000 |  |  | $ 9,718,000 |
Troubled Debt Restructurings [Member] | Covid Nineteen [Member] |  |  |  |  |
Loans and Allowance for Credit Losses [Line Items] |  |  |  |  |
Investment recorded post modification | $ 66,700,000 |  |  |  |
Troubled Debt Restructurings [Member] | Modification one [Member] | Covid Nineteen [Member] |  |  |  |  |
Loans and Allowance for Credit Losses [Line Items] |  |  |  |  |
Number of Modifications | Loans | 122 |  |  |  |
Financing Receivable, Modifications, Post-Modification Recorded Investment | $ 64,200,000 |  |  |  |
Troubled Debt Restructurings [Member] | Modification Two [Member] | Covid Nineteen [Member] |  |  |  |  |
Loans and Allowance for Credit Losses [Line Items] |  |  |  |  |
Number of Modifications | Loans | 118 |  |  |  |
Financing Receivable, Modifications, Post-Modification Recorded Investment | $ 2,500,000 |  |  |  |
Foreclosure [Member] | Troubled Debt Restructurings [Member] |  |  |  |  |
Loans and Allowance for Credit Losses [Line Items] |  |  |  |  |
Number of default loans | SecurityLoan |  |  |  | 0 |
Non troubled debt restructuring [Member] | Covid Nineteen [Member] | Financing receivables, 30 to 59 days past due [Member] |  |  |  |  |
Loans and Allowance for Credit Losses [Line Items] |  |  |  |  |
Financing receivable number of days past due |  |  | 30 days |  |
Period of loan excecution | 60 days |  |  |  |

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