Fair Value - Summary of Additional Quantitative Information about Assets Measured at Fair Value on Nonrecurring Basis (Detail) - Fair Value, Measurements, Nonrecurring [Member] - Level III [Member] $ in Thousands	Sep. 30, 2024 USD ($)	Sep. 30, 2023 USD ($)
Individually Evaluated Loans Held For Investment [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Estimate	$ 7,615
Servicing Asset, Valuation Technique [Extensible Enumeration]	us-gaap:MarketApproachValuationTechniqueMember
Servicing Asset, Measurement Input [Extensible Enumeration]	us-gaap:MeasurementInputAppraisedValueMember
Individually Evaluated Loans Held For Investment [Member] | Minimum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value input appraisal adjustments	0
Individually Evaluated Loans Held For Investment [Member] | Maximum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value input appraisal adjustments	0.35
Individually Evaluated Loans Held For Investment [Member] | Weighted Average [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value input appraisal adjustments	0.209
Impaired Loans [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Estimate		$ 9,693
Servicing Asset, Valuation Technique [Extensible Enumeration]		us-gaap:MarketApproachValuationTechniqueMember
Servicing Asset, Measurement Input [Extensible Enumeration]		us-gaap:MeasurementInputAppraisedValueMember
Impaired Loans [Member] | Minimum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value input appraisal adjustments		0
Impaired Loans [Member] | Maximum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value input appraisal adjustments		0.35
Impaired Loans [Member] | Weighted Average [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value input appraisal adjustments		0.208
Foreclosed Real Estate Owned [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Estimate	$ 3,195	$ 3,311
Servicing Asset, Valuation Technique [Extensible Enumeration]	us-gaap:MarketApproachValuationTechniqueMember	us-gaap:MarketApproachValuationTechniqueMember
Servicing Asset, Measurement Input [Extensible Enumeration]	us-gaap:MeasurementInputAppraisedValueMember	us-gaap:MeasurementInputAppraisedValueMember
Fair value input appraisal adjustments	0.10
Foreclosed Real Estate Owned [Member] | Minimum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value input appraisal adjustments		0.10
Foreclosed Real Estate Owned [Member] | Maximum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value input appraisal adjustments		0.35
Foreclosed Real Estate Owned [Member] | Weighted Average [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value input appraisal adjustments	0.10	0.102