Loans Receivable, Net and Allowance for Loan Losses - Summary of Troubled Debt Restructuring Granted (Detail) $ in Thousands	3 Months Ended	6 Months Ended
Mar. 31, 2021 USD ($) Contract	Mar. 31, 2020 Contract	Mar. 31, 2021 USD ($) Contract	Mar. 31, 2020 USD ($) Contract
Financing Receivable, Modifications [Line Items]
Number of Contracts \| Contract		0
Real Estate Loans [Member] \| Residential [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts \| Contract	1		1	1
Pre-Modification Outstanding Recorded Investment	$ 75		$ 75	$ 540
Post-Modification Outstanding Recorded Investment	$ 75		$ 75	$ 540
Troubled Debt Restructurings [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts \| Contract	1		1	1
Pre-Modification Outstanding Recorded Investment	$ 75		$ 75	$ 540
Post-Modification Outstanding Recorded Investment	$ 75		$ 75	$ 540

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

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- Definition

Number of financing receivables that have been modified by troubled debt restructurings.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 33
-URI http://asc.fasb.org/extlink&oid=121611835&loc=SL6953676-111524

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- Definition

Amount, after troubled debt restructuring, of modified financing receivable.

+ References

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- Definition

Amount, before troubled debt restructuring, of financing receivable to be modified.

+ References

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