Earnings Per Share - Composition of the Weighted-Average Common Shares (Denominator) Used in the Basic and Diluted Earnings per Share Computation (Detail) - shares	12 Months Ended
Sep. 30, 2022	Sep. 30, 2021
Earnings Per Share [Abstract]
Weighted-average common shares outstanding	18,133,095	18,133,095
Average treasury stock shares	(7,668,387)	(7,431,752)
Average unearned ESOP shares	(656,281)	(701,545)
Average unearned nonvested shares	(46,990)	(54,270)
Weighted-average common shares and common stock equivalents used to calculate basic earnings per share	9,761,437	9,945,528
Additional common stock equivalents (nonvested stock) used to calculate diluted earnings per share	3,720	1,976
Weighted-average common shares and common stock equivalents used to calculate diluted earnings per share	9,765,157	9,947,504

Additional common stock equivalents non vested stock used to calculate diluted earnings per share.

No definition available.

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- Definition

Weighted average number of shares unearned non vested shares.

+ References

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- Definition

The average number of shares or units issued and outstanding that are used in calculating diluted EPS or earnings per unit (EPU), determined based on the timing of issuance of shares or units in the period.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=124432515&loc=d3e3550-109257

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 45
-Paragraph 16
-URI https://asc.fasb.org/extlink&oid=126958026&loc=d3e1505-109256

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- Definition

Number of employee stock ownership plan (ESOP) shares that have not been committed to be released determined by relating the portion of time within a reporting period that these shares have been outstanding to the total time in that period.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 40
-Section 45
-Paragraph 3
-URI https://asc.fasb.org/extlink&oid=109244644&loc=d3e17400-113927

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- Definition

This element represents the weighted average total number of shares issued throughout the period including the first (beginning balance outstanding) and last (ending balance outstanding) day of the period before considering any reductions (for instance, shares held in treasury) to arrive at the weighted average number of shares outstanding. Weighted average relates to the portion of time within a reporting period that common shares have been issued and outstanding to the total time in that period. Such concept is used in determining the weighted average number of shares outstanding for purposes of calculating earnings per share (basic).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 45
-Paragraph 10
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- Definition

Number of [basic] shares or units, after adjustment for contingently issuable shares or units and other shares or units not deemed outstanding, determined by relating the portion of time within a reporting period that common shares or units have been outstanding to the total time in that period.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=124432515&loc=d3e3550-109257

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-Section 45
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- Definition

Number of shares of treasury stock determined by relating the portion of time within a reporting period that treasury shares have been outstanding to the total time in that period. Treasury stock is stock that the Entity has issued but subsequently reacquired.

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