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, 2018 USD ($) Contract	Mar. 31, 2017 USD ($) Contract	Mar. 31, 2018 USD ($) Contract	Mar. 31, 2017 USD ($) Contract
Financing Receivable, Modifications [Line Items]
Number of Contracts \| Contract		3		5
Real Estate Loans [Member] \| Residential [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts \| Contract		1	2	3
Pre-Modification Outstanding Recorded Investment		$ 135	$ 243	$ 379
Post-Modification Outstanding Recorded Investment		$ 135	$ 235	$ 379
Real Estate Loans [Member] \| Commercial Real Estate Loans [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts \| Contract	1	1	1	1
Pre-Modification Outstanding Recorded Investment	$ 107	$ 132	$ 107	$ 132
Post-Modification Outstanding Recorded Investment	$ 107	$ 132	$ 107	$ 132
Auto Loans [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts \| Contract	1		1
Pre-Modification Outstanding Recorded Investment	$ 15		$ 15
Post-Modification Outstanding Recorded Investment	$ 15		$ 15
Other [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts \| Contract		1		1
Pre-Modification Outstanding Recorded Investment		$ 24		$ 24
Post-Modification Outstanding Recorded Investment		$ 24		$ 24
Troubled Debt Restructurings [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts \| Contract	2	3	4	5
Pre-Modification Outstanding Recorded Investment	$ 122	$ 291	$ 365	$ 535
Post-Modification Outstanding Recorded Investment	$ 122	$ 291	$ 357	$ 535

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 33
-URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953676-111524

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Post-modification amount of investment in financing receivables modified by troubled debt restructurings.

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Pre-modification amount of investment in financing receivables modified by troubled debt restructurings.

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