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Derivatives and Hedging Activities - Additional Information (Detail) - USD ($) |  |  |  | 3 Months Ended | 9 Months Ended |  |  |  |  |  |  |
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Jun. 06, 2025 | Dec. 19, 2024 | Nov. 01, 2024 | Sep. 30, 2025 | Sep. 30, 2025 | Sep. 30, 2024 | Sep. 10, 2025 | Jun. 23, 2025 | Dec. 31, 2024 | Jul. 12, 2024 | Dec. 31, 2023 | Nov. 30, 2023 | Jun. 30, 2023
Derivatives Fair Value [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Interest rate swaps |  |  |  |  | $ (8,000) | $ (152,000) |  |  |  |  |  |  |
Cash in collateral returned |  |  |  | $ 19,573,000 | 19,573,000 |  |  |  | $ 7,100,000 |  |  |  |
Designated as Hedging Instrument [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Derivatives Fair Value [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Notional amount |  |  |  | 0 | 0 |  |  |  |  | $ 10,000,000 |  |  |
Carrying amount of savings deposit |  |  |  | $ 22,000,000 | $ 22,000,000 |  |  |  | $ 22,100,000 |  |  |  |
Cash Flow Hedges on 90-day Advances from FHLB [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Derivatives Fair Value [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Average fixed interest rate |  |  |  |  |  |  |  |  |  | 4.33% |  |  |
Fixed annual rate |  |  |  | 4.38% | 4.38% |  |  |  |  | 5.32% |  |  |
Fair Value Hedging [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Derivatives Fair Value [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Remaining maturity |  |  |  | 1 year 2 months 12 days | 1 year 2 months 12 days |  |  |  | 1 year 5 months 1 day |  |  |  |
Average fixed interest rate |  |  |  | 3.70% | 3.70% |  |  |  | 3.99% |  |  |  |
Fixed annual rate |  |  |  | 4.38% | 4.38% |  |  |  | 5.19% |  |  |  |
Amortized over remaining expected life of original swap |  |  | 24 months |  |  |  |  |  |  |  |  |  |
Loans [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Derivatives Fair Value [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Cumulative amount of fair value hedging adjustment included in the carrying amount of the hedged assets/(liabilities) |  |  |  | $ 80,000 | $ 80,000 |  |  |  | $ (43,000) |  |  |  |
Carrying amount of savings deposit |  |  |  | 50,080,000 | 50,080,000 |  |  |  | 24,957,000 |  |  |  |
Loans [Member] | Designated as Hedging Instrument [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Derivatives Fair Value [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Designated hedged items |  |  |  | 25,000,000 | 25,000,000 |  |  |  |  |  |  |  |
Loans [Member] | Fair Value Hedging [Member] | Fixed Rate Assets [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Derivatives Fair Value [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Cumulative amount of fair value hedging adjustment included in the carrying amount of the hedged assets/(liabilities) |  |  |  | 80,000 | 80,000 |  |  |  |  |  | $ (43,000) |  |
Interest Rate Contract [Member] | Cash Flow Hedges on 90-day Advances from FHLB [Member] | Designated as Hedging Instrument [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Derivatives Fair Value [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Notional amount |  |  |  | $ 0 | $ 0 |  |  |  |  |  |  |  |
Interest Rate Contract [Member] | Fair Value Hedging [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Derivatives Fair Value [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Cash in collateral returned | $ 336,000 | $ 280,000 | $ 1,200,000 |  |  |  |  |  |  |  |  |  |
Average fixed interest rate |  |  |  | 4.38% | 4.38% |  | 3.62% | 3.78% |  |  |  |  |
Fixed annual rate |  |  |  |  |  |  | 4.37% | 4.31% |  |  |  |  |
Interest Rate Contract [Member] | Fair Value Hedging [Member] | Designated as Hedging Instrument [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Derivatives Fair Value [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Notional amount |  |  |  | $ 0 | $ 0 |  | $ 25,000,000 | $ 25,000,000 |  |  | $ 10,000,000 | $ 25,000,000 | $ 25,000,000
Interest Rate Swap Contracts and Customer Loan Swaps [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Derivatives Fair Value [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Cash collateral from counterparties |  |  |  | 450,000 | 450,000 |  |  |  | $ 781,000 |  |  |  |
Fixed Interest Rate Swap [Member] | Designated as Hedging Instrument [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Derivatives Fair Value [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Interest rate swaps |  |  |  | 4,000,000 | (8,000,000) |  |  |  |  |  |  |  |
Interest rate swap interest income reclassified from AOCI into expense |  |  |  | $ 0 | $ 0 |  |  |  |  |  |  |  |
Fixed Interest Rate Swap [Member] | Fair Value Hedging [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Derivatives Fair Value [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Payment to counterparty in swap termination fee | $ 0 | 32,000 | 398,000 |  |  |  |  |  |  |  |  |  |
Fixed Interest Rate Swap [Member] | Fair Value Hedging [Member] | Residential mortgage backed securities [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Derivatives Fair Value [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Payment to counterparty in swap termination fee |  | $ 32,000 | $ 398,000 |  |  |  |  |  |  |  |  |  |

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