Investment Securities (Additional Information) (Detail) - USD ($)	3 Months Ended
Dec. 31, 2018	Dec. 31, 2017
Schedule of Available-for-sale Securities [Line Items]
Net gain (loss) on trading account securities	$ 0	$ 150,000
Investments, Fair Value Disclosure	$ 36,000
Two Privately Issued Collateralized Mortgage Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Available for sale debt securities in loss position, depreciation percentage	9.45%
Unrealized Gain (Loss) on Securities	$ 4,000
Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available for sale debt securities in loss position, depreciation percentage	97.94%
Debt Securities [Member] \| Downgraded Due To Potential Credit Losses [Member]
Schedule of Available-for-sale Securities [Line Items]
Carrying Value Of Downgraded Due To Potential Credit Losses	$ 1,200,000
Debt Securities [Member] \| Downgraded Privately Issued CMOs [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Market Value Of Downgraded Privately Issued Collateralized Mortgage Obligations	$ 1,500,000

The element represents about the carrying value of downgraded due to potential credit losses.

No definition available.

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- Definition

The elements represents about the fair market value of downgraded privately issued collateralized mortgage obligations.

+ References

No definition available.

+ Details

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- Definition

Percent of Total Unrealized Loss to Total Amortized Cost Basis

+ References

No definition available.

+ Details

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- Definition

Fair value portion of investment securities, including, but not limited to, marketable securities, derivative financial instruments, and investments accounted for under the equity method.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=99377789&loc=d3e19207-110258

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- Definition

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.

+ References

No definition available.

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- Definition

Amount of gain (loss) realized from securities classified as trading.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of unrealized gain (loss) recognized in the income statement on unsold other securities.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3602-108585

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