BORROWINGS - Narrative (Details)	12 Months Ended
Dec. 31, 2024 USD ($) bank	Dec. 31, 2023 USD ($) bank	Oct. 11, 2023 USD ($)
Debt Instrument [Line Items]
Residential real estate loans and securities pledged as collateral for FHLB advances, carrying value		$ 824,000,000.0
FHLB stock	$ 18,000,000.0	18,000,000.0
FHLB borrowing capacity, authorized	800,000,000.0	800,000,000.0
Commercial loans pledged as collateral for federal reserve discount window	1,710,000,000	1,590,000,000
Federal reserve borrowing capacity	1,360,000,000	1,260,000,000
Remaining borrowing capacity	$ 395,000,000	$ 325,000,000.0
Number of banks \| bank	13	11
Amount drawn	$ 0	$ 0
American Financial Exchange
Debt Instrument [Line Items]
Remaining borrowing capacity	304,000,000.0	319,000,000.0
Amount drawn	0	$ 0
Pledged as Collateral
Debt Instrument [Line Items]
Securities borrowed collateral value	150,500,000
FHLB of Indianapolis Bullet Advance
Debt Instrument [Line Items]
Interest rate (as a percent)		5.55%
Federal Home Loan Bank Advances
Debt Instrument [Line Items]
Current borrowing capacity	555,900,000	$ 555,900,000
Borrowings	0	0
Line of Credit
Debt Instrument [Line Items]
Borrowings	$ 0	$ 0
Line of Credit \| Unsecured Revolving Credit Agreement
Debt Instrument [Line Items]
Borrowing capacity			$ 30,000,000
Debt instrument, term	1 year

The amount authorized to borrow from the Federal Home Loan Bank.

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The amount authorized to borrow from the Federal Reserve Bank.

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Line Of Credit Facility, Remaining Borrowing Capacity, Number Of Banks

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The carrying amount as of the date of the latest financial statement presented of commercial loans which are owned but transferred to the Federal Reserve to serve as collateral to partially or fully secure a debt obligation and for which the transferee does not have the right by contract or custom to sell or re-pledge them to an unrelated party.

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The carrying amount as of the date of the latest financial statement presented of residential mortgage loans and mortgage-related securities classified as available for sale which are owned but transferred to the FHLB to serve as collateral to partially or fully secure a debt obligation and for which the transferee does not have the right by contract or custom to sell or re-pledge them to an unrelated party.

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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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Period of time between issuance and maturity of debt instrument, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Rate of interest applicable on advance from Federal Home Loan Bank (FHLBank).

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Federal Home Loan Bank (FHLB) stock represents an equity interest in a FHLB. It does not have a readily determinable fair value because its ownership is restricted and it lacks a market (liquidity).

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The aggregate fair value as of the balance sheet date of financial instruments and other positions owned by the entity including: (1) mortgages, mortgage-backed and asset backed securities; (2) US government and agency obligations; (3) state and municipal government obligations; (4) other sovereign government debt; (5) corporate obligations; (6) corporate equities; (7) principal investments; (8) derivative contracts; and (9) physical commodities. Includes both pledged and unpledged holdings.

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The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

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Amount of current borrowing capacity under the credit facility considering any current restrictions on the amount that could be borrowed (for example, borrowings may be limited by the amount of current assets), but without considering any amounts currently outstanding under the facility.

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Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

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Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

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Reflects the total carrying amount as of the balance sheet date of debt having initial terms less than one year or the normal operating cycle, if longer.

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