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Junior Subordinated Debentures - Issuance (Details) - USD ($) $ in Thousands	1 Months Ended	6 Months Ended
	Apr. 30, 2007	Jun. 30, 2025	Jun. 15, 2017	Dec. 31, 2024	Jun. 30, 2024
Junior subordinated debentures
Junior subordinated debentures		$ 25,774		$ 25,773
Old Second Capital Trust II
Junior subordinated debentures
Proceeds from sale of cumulative trust preferred securities	$ 25,000
Maturity Period		30 years
Cash distribution fixed rate of trust preferred securities (as a percent)			6.77%
Basis points added to cash distribution floating rate base (as a percent)		1.50%
Cash distribution, floating rate base		three-month SOFR
Amortization period		30 years
Old Second Capital Trust II | Debt Instrument, Redemption, Period One
Junior subordinated debentures
Interest rate (as a percent)		4.48%			4.49%
Junior Subordinated Debentures
Junior subordinated debentures
Junior Subordinated Debentures issuance cost		$ 1,000		$ 1,000
Junior Subordinated Debentures | Old Second Capital Trust II
Junior subordinated debentures
Junior subordinated debentures		$ 25,800

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The percentage points added to the reference rate to compute the variable rate on the trust preferred securities.

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Contractual interest rate for funds borrowed, under the debt agreement.

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Including the current and noncurrent portions, the carrying value of junior subordinated long-term debt owed to unconsolidated subsidiary trusts as of the balance sheet date. Such debt places a lender in a lien position behind debt having a higher priority of repayment in liquidation of the entity's assets and was initially scheduled to be repaid after one year or beyond the normal operating cycle if longer.

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The cash inflow from issuance of preferred stocks by a business trust or other special purpose entity, mainly established by a bank holding entity, to third party investors. The trust's assets are deeply subordinated debentures of the bank holding entity. Most trust preferred securities are subject to a mandatory redemption upon the repayment of the debentures.

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