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Fair Values of Assets and Liabilities - Summary of Significant Unobservable Inputs used in Level 3 Assets Measured at Fair Value on Recurring Basis (Detail) - Fair Value, Inputs, Level 3 [Member] - Fair Value, Measurements, Recurring [Member] $ in Thousands | 9 Months Ended | 12 Months Ended |  |
--- | --- | --- | --- | ---
Sep. 30, 2025 USD ($) | Dec. 31, 2024 USD ($) | Sep. 30, 2024 USD ($) | Dec. 31, 2023 USD ($)
Mortgage servicing rights [Member] |  |  |  |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |  |  |  |
Mortgage Servicing Rights | [1] | $ 267 | $ 305 | $ 308 | $ 339
Prepayment Rate [Member] | Mortgage servicing rights [Member] |  |  |  |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |  |  |  |
Servicing Asset, Valuation Technique [Extensible List] |  | us-gaap:ValuationTechniqueDiscountedCashFlowMember | us-gaap:ValuationTechniqueDiscountedCashFlowMember |  |
Mortgage Servicing Rights |  | $ 267 | $ 305 |  |
Prepayment Rate [Member] | Minimum [Member] |  |  |  |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |  |  |  |
Mortgage Servicing Rights, Measuring Inputs |  | 0.0467 | 0.0454 |  |
Prepayment Rate [Member] | Maximum [Member] |  |  |  |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |  |  |  |
Mortgage Servicing Rights, Measuring Inputs |  | 0.254 | 0.1871 |  |
Prepayment Rate [Member] | Weighted Average [Member] |  |  |  |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |  |  |  |
Mortgage Servicing Rights, Measuring Inputs | [2] | 0.0903 | 0.0651 |  |
Fair value valuation techniques |  | Prepayment Rate | Prepayment Rate |  |
Discount Rate [Member] | Minimum [Member] |  |  |  |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |  |  |  |
Mortgage Servicing Rights, Measuring Inputs |  | 0.095 | 0.10 |  |
Discount Rate [Member] | Maximum [Member] |  |  |  |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |  |  |  |
Mortgage Servicing Rights, Measuring Inputs |  | 0.095 | 0.10 |  |
Discount Rate [Member] | Weighted Average [Member] |  |  |  |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |  |  |  |
Mortgage Servicing Rights, Measuring Inputs | [2] | 0.0950 | 0.1000 |  |
Fair value valuation techniques |  | Discount Rate | Discount Rate |  |
Delinquency Rate [Member] | Minimum [Member] |  |  |  |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |  |  |  |
Mortgage Servicing Rights, Measuring Inputs |  | 0.0211 | 0.0217 |  |
Delinquency Rate [Member] | Maximum [Member] |  |  |  |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |  |  |  |
Mortgage Servicing Rights, Measuring Inputs |  | 0.0252 | 0.0264 |  |
Delinquency Rate [Member] | Weighted Average [Member] |  |  |  |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |  |  |  |
Mortgage Servicing Rights, Measuring Inputs | [2] | 0.0218 | 0.0225 |  |
Fair value valuation techniques |  | Delinquency Rate | Delinquency Rate |  |
Default Rate [Member] | Minimum [Member] |  |  |  |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |  |  |  |
Mortgage Servicing Rights, Measuring Inputs |  | 0.0014 | 0.0014 |  |
Default Rate [Member] | Maximum [Member] |  |  |  |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |  |  |  |
Mortgage Servicing Rights, Measuring Inputs |  | 0.0024 | 0.0024 |  |
Default Rate [Member] | Weighted Average [Member] |  |  |  |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |  |  |  |
Mortgage Servicing Rights, Measuring Inputs | [2] | 0.0016 | 0.0016 |  |
Fair value valuation techniques |  | Default Rate | Default Rate |  |
[1] | Realized and unrealized gains and losses related to mortgage servicing rights are reported as a component of loan servicing fee income in the Company’s consolidated statements of income (loss).
[2] | Unobservable inputs for mortgage servicing rights were weighted by loan amount.

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