Derivatives, Hedging Activities and Financial Instruments with Off-Balance Sheet Risk - Fair Value of Derivatives (Details)	9 Months Ended	12 Months Ended
Sep. 30, 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	$ 3,600,000	$ 7,300,000
Number of financial institutions in which cash collateral pledged \| item	2	2
Interest Rate Swap
Financial Instruments with Off-Balance Sheet Risk and Derivative Transactions
Cash collateral pledged with financial institutions, dollars	$ 2,600,000	$ 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	$ 2,165,000	$ 2,576,000
Derivative liabilities designated as hedging instruments, fair value	2,041,000	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	2,165,000	2,576,000
Derivative liabilities designated as hedging instruments, fair value	2,041,000	$ 5,598,000
Not Designated as Hedging Instrument
Financial Instruments with Off-Balance Sheet Risk and Derivative Transactions
Derivative assets designated as hedging instruments, fair value	2,481,000
Derivative liabilities designated as hedging instruments, fair value	$ 2,348,000
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	14	17
Notional amount	$ 153,443,000	$ 104,777,000
Derivative assets designated as hedging instruments, fair value	2,334,000	2,726,000
Derivative liabilities designated as hedging instruments, fair value	2,334,000	2,726,000
Not Designated as Hedging Instrument \| Interest Rate Swap
Financial Instruments with Off-Balance Sheet Risk and Derivative Transactions
Notional amount	120,500,000	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	$ 18,800,000	$ 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	57	4
Notional amount	$ 18,816,000	$ 44,790,000
Derivative assets designated as hedging instruments, fair value	$ 70,000	$ 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	5
Notional amount	$ 57,184,000
Derivative assets designated as hedging instruments, fair value	77,000	2,805,000
Derivative liabilities designated as hedging instruments, fair value	14,000	$ 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	2,000,000.0
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	$ 327,000

Represents the number of financial institutions in which cash collateral pledged.

No definition available.

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- Definition

Carrying amount as of the balance sheet date of cash collateral held for borrowed securities, for which the cash is restricted as to withdrawal or usage.

+ References

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-Name Accounting Standards Codification
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- Definition

Fair value of all asset derivatives designated as cash flow hedging instruments.

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- Definition

Fair value of all liability derivatives designated as cash flow hedging instruments.

+ References

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Amount, after allowance for credit loss, of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), investment in debt security measured at amortized cost (held-to-maturity), and investment in debt security measured at fair value with change in fair value recognized in net income (trading).

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Nominal or face amount used to calculate payment on derivative.

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- Definition

The number of derivative instruments of a particular group held by the entity.

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The estimated net amount of unrealized gains or losses on interest rate cash flow hedges as of the balance sheet date expected to be reclassified to earnings within the next twelve months.

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