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Derivatives, Hedging Activities and Financial Instruments with Off-Balance Sheet Risk - Fair Value of Derivatives (Details) | 6 Months Ended | 12 Months Ended |
--- | --- | --- | ---
Jun. 30, 2024 USD ($) item | Dec. 31, 2023 USD ($) item | Mar. 31, 2023 USD ($)
Two financial institutions |  |  |
Financial Instruments with Off-Balance Sheet Risk and Derivative Transactions |  |  |
Cash collateral pledged with financial institutions, dollars | $ 6,800,000 | $ 7,300,000 |
Number of financial institutions in which cash collateral pledged | item |  | 2 |
Interest Rate Swap |  |  |
Financial Instruments with Off-Balance Sheet Risk and Derivative Transactions |  |  |
Cash collateral pledged with financial institutions, dollars | 5,400,000 |  | $ 4,100,000
Investment securities pledged with financial institutions, dollars | $ 0 | $ 0 |
Number of financial institutions in which cash collateral pledged | item | 1 | 1 |
Designated as Hedging Instrument |  |  |
Financial Instruments with Off-Balance Sheet Risk and Derivative Transactions |  |  |
Derivative assets designated as hedging instruments, fair value | $ 3,618,000 | $ 2,576,000 |
Derivative liabilities designated as hedging instruments, fair value | 5,394,000 | 5,598,000 |
Designated as Hedging Instrument | Interest Rate Products | 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 |
Designated as Hedging Instrument | Interest Rate Products | 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 |
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 |
Notional amount | $ 325,774,000 | $ 325,774,000 |
Derivative assets designated as hedging instruments, fair value | 3,618,000 |  |
Derivative liabilities designated as hedging instruments, fair value | 5,394,000 | 5,598,000 |
Designated as Hedging Instrument | Interest Rate Swap | OSBC Affiliates |  |  |
Financial Instruments with Off-Balance Sheet Risk and Derivative Transactions |  |  |
Derivative assets designated as hedging instruments, fair value |  | $ 2,576,000 |
Not Designated as Hedging Instrument |  |  |
Financial Instruments with Off-Balance Sheet Risk and Derivative Transactions |  |  |
Derivative assets designated as hedging instruments, fair value | 2,541,000 |  |
Derivative liabilities designated as hedging instruments, fair value | $ 2,441,000 |  |
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 | 16 | 17 |
Notional amount | $ 130,775,000 | $ 104,777,000 |
Derivative assets designated as hedging instruments, fair value | 2,433,000 | 2,726,000 |
Derivative liabilities designated as hedging instruments, fair value | 2,433,000 | 2,726,000 |
Not Designated as Hedging Instrument | Interest Rate Swap |  |  |
Financial Instruments with Off-Balance Sheet Risk and Derivative Transactions |  |  |
Notional amount | 97,900,000 | 104,800,000 |
Not Designated as Hedging Instrument | Interest rate cap |  |  |
Financial Instruments with Off-Balance Sheet Risk and Derivative Transactions |  |  |
Notional amount | 32,900,000 | 0 |
Not Designated as Hedging Instrument | Commitments. |  |  |
Financial Instruments with Off-Balance Sheet Risk and Derivative Transactions |  |  |
Notional amount | $ 13,700,000 | $ 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 | 45 | 4 |
Notional amount | $ 13,687,000 | $ 44,790,000 |
Derivative assets designated as hedging instruments, fair value | $ 64,000 | $ 89,000 |
Not Designated as Hedging Instrument | Interest Rate Lock Commitments and Forward Contracts. | Commercial Loan Customers |  |  |
Financial Instruments with Off-Balance Sheet Risk and Derivative Transactions |  |  |
Derivative, number of transactions | item |  | 24 |
Notional amount |  | $ 8,375,000 |
Derivative liabilities designated as hedging instruments, fair value |  | 10,000 |
Not Designated as Hedging Instrument | Other Contracts |  |  |
Financial Instruments with Off-Balance Sheet Risk and Derivative Transactions |  |  |
Derivative, number of transactions | item | 4 |  |
Notional amount | $ 39,021,000 |  |
Derivative assets designated as hedging instruments, fair value | 44,000 | 2,805,000 |
Derivative liabilities designated as hedging instruments, fair value | 8,000 | $ 2,726,000 |
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 | 5,100,000 |  |
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 | $ 608,000 |  |

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