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Financial Instruments with Off-Balance Sheet Risk and Derivative Transactions - Fair Value of Derivatives (Details) | 12 Months Ended
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Dec. 31, 2024 USD ($) item | Dec. 31, 2024 USD ($) item | Dec. 31, 2023 USD ($) item
Two financial institutions |  |  |
Financial Instruments with Off-Balance Sheet Risk and Derivative Transactions |  |  |
Cash collateral pledged with financial institutions, dollars | $ 2,300,000 | $ 2,300,000 | $ 7,300,000
Number of financial institutions in which cash collateral pledged | item |  | 1 | 2
Interest Rate Swap |  |  |
Financial Instruments with Off-Balance Sheet Risk and Derivative Transactions |  |  |
Investment securities pledged with financial institutions, dollars | $ 0 | $ 0 | $ 0
Number of financial institutions in which cash collateral pledged | 5,200,000 | 2 | 1
Interest Rate Swap | Two financial institutions |  |  |
Financial Instruments with Off-Balance Sheet Risk and Derivative Transactions |  |  |
Cash collateral pledged with financial institutions, dollars |  |  | $ 4,100,000
Designated as Hedging Instrument |  |  |
Financial Instruments with Off-Balance Sheet Risk and Derivative Transactions |  |  |
Derivative assets designated as hedging instruments, fair value | $ 3,823,000 | $ 3,823,000 | 2,576,000
Derivative liabilities designated as hedging instruments, fair value | $ 1,512,000 | $ 1,512,000 | $ 5,598,000
Designated as Hedging Instrument | Interest Rate Products | OSBC Affiliates |  |  |
Financial Instruments with Off-Balance Sheet Risk and Derivative Transactions |  |  |
Derivative, number of transactions | item | 5 | 5 | 5
Notional amount | $ 325,774,000 | $ 325,774,000 | $ 325,774,000
Derivative assets designated as hedging instruments, fair value | 3,823,000 | 3,823,000 | 2,576,000
Derivative liabilities designated as hedging instruments, fair value | 1,512,000 | 1,512,000 | 5,598,000
Designated as Hedging Instrument | Interest Rate Swap | Cash flow hedges of certain variable rate commercial and commercial real estate loan pools |  |  |
Financial Instruments with Off-Balance Sheet Risk and Derivative Transactions |  |  |
Notional amount | 300,000,000.0 | 300,000,000.0 | 300,000,000.0
Designated as Hedging Instrument | Interest Rate Swap | Cash flow hedge of junior subordinated debentures and was executed to pay fixed and receive variable rate cash flows |  |  |
Financial Instruments with Off-Balance Sheet Risk and Derivative Transactions |  |  |
Notional amount | 25,800,000 | 25,800,000 | 25,800,000
Not Designated as Hedging Instrument |  |  |
Financial Instruments with Off-Balance Sheet Risk and Derivative Transactions |  |  |
Derivative assets designated as hedging instruments, fair value | 1,758,000 | 1,758,000 | 2,805,000
Derivative liabilities designated as hedging instruments, fair value | $ 1,680,000 | $ 1,680,000 | $ 2,726,000
Not Designated as Hedging Instrument | Interest Rate Products | Commercial Loan Customers |  |  |
Financial Instruments with Off-Balance Sheet Risk and Derivative Transactions |  |  |
Derivative, number of transactions | item | 13 | 13 | 17
Notional amount | $ 154,137,000 | $ 154,137,000 | $ 104,777,000
Derivative assets designated as hedging instruments, fair value | 1,675,000 | 1,675,000 | 2,726,000
Derivative liabilities designated as hedging instruments, fair value | 1,675,000 | 1,675,000 | 2,726,000
Not Designated as Hedging Instrument | Interest Rate Swap |  |  |
Financial Instruments with Off-Balance Sheet Risk and Derivative Transactions |  |  |
Notional amount | 121,200,000 | 121,200,000 | 104,800,000
Not Designated as Hedging Instrument | Commitments. |  |  |
Financial Instruments with Off-Balance Sheet Risk and Derivative Transactions |  |  |
Notional amount | $ 8,700,000 | $ 8,700,000 | $ 8,400,000
Not Designated as Hedging Instrument | Interest Rate Lock Commitments and Forward Contracts. |  |  |
Financial Instruments with Off-Balance Sheet Risk and Derivative Transactions |  |  |
Derivative, number of transactions | item | 30 | 30 | 24
Notional amount | $ 8,667,000 | $ 8,667,000 | $ 8,375,000
Derivative assets designated as hedging instruments, fair value | $ 55,000 | $ 55,000 | $ 10,000
Not Designated as Hedging Instrument | Other Contracts |  |  |
Financial Instruments with Off-Balance Sheet Risk and Derivative Transactions |  |  |
Derivative, number of transactions | item | 5 | 5 | 4
Notional amount | $ 58,259,000 | $ 58,259,000 | $ 44,790,000
Derivative assets designated as hedging instruments, fair value | 28,000 | 28,000 | 89,000
Derivative liabilities designated as hedging instruments, fair value | 5,000 | 5,000 |
Not Designated as Hedging Instrument | Forward Contracts |  |  |
Financial Instruments with Off-Balance Sheet Risk and Derivative Transactions |  |  |
Notional amount | 5,500,000 | 5,500,000 | $ 6,000,000
Interest Income |  |  |
Financial Instruments with Off-Balance Sheet Risk and Derivative Transactions |  |  |
Amount to be reclassified as an decrease to interest expense during the next twelve months | 404,000 | 404,000 |
Interest Expense |  |  |
Financial Instruments with Off-Balance Sheet Risk and Derivative Transactions |  |  |
Amount to be reclassified as an decrease to interest expense during the next twelve months | $ 1,500,000 | $ 1,500,000 |

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