Securities - Amortized Cost and Fair Value (Details) $ in Thousands	3 Months Ended
Mar. 31, 2025 USD ($) item	Dec. 31, 2024 USD ($)
Securities Available-for-Sale
Amortized Cost	$ 1,206,417	$ 1,230,328
Gross Unrealized Gains	2,448	2,152
Gross Unrealized Losses	(62,144)	(70,779)
Fair Value	1,146,721	1,161,701
Accrued interest receivable	7,100
FHLB and FRB Stock
FHLBC stock	4,500	4,500
FRBC stock	14,900	14,900
Securities pledged to secure deposits and for other purposes	$ 638,500	717,500
Other disclosures
Number of securities issued from originators \| item	0
Number of originators \| item	1
Minimum percentage of securities investment	10.00%
U.S. Treasury
Securities Available-for-Sale
Amortized Cost	$ 159,077	193,902
Gross Unrealized Gains	1,114	700
Gross Unrealized Losses		(459)
Fair Value	160,191	194,143
U.S. government agencies
Securities Available-for-Sale
Amortized Cost	39,033	39,202
Gross Unrealized Losses	(986)	(1,388)
Fair Value	38,047	37,814
U.S. government agencies mortgage-backed
Securities Available-for-Sale
Amortized Cost	108,678	112,241
Gross Unrealized Losses	(9,749)	(11,964)
Fair Value	98,929	100,277
States and political subdivisions
Securities Available-for-Sale
Amortized Cost	220,492	226,969
Gross Unrealized Gains	136	264
Gross Unrealized Losses	(11,511)	(11,777)
Fair Value	209,117	215,456
Collateralized mortgage obligations
Securities Available-for-Sale
Amortized Cost	428,319	411,170
Gross Unrealized Gains	775	647
Gross Unrealized Losses	(38,203)	(43,201)
Fair Value	390,891	368,616
Asset-backed Securities
Securities Available-for-Sale
Amortized Cost	51,115	64,215
Gross Unrealized Gains	230	69
Gross Unrealized Losses	(1,644)	(1,981)
Fair Value	49,701	62,303
Collateralized loan obligations.
Securities Available-for-Sale
Amortized Cost	199,703	182,629
Gross Unrealized Gains	193	472
Gross Unrealized Losses	(51)	(9)
Fair Value	$ 199,845	$ 183,092

Represents the minimum percentage of securities investment from originators.

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Represents the number of originators that the company has invested over 10 % of its stockholders equity.

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Represents the number of securities issued from originators.

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Interest, dividends, rents, ancillary and other revenues earned but not yet received by the entity on its investments.

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Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amortized cost excluding accrued interest, before 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).

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Amount excluding accrued interest, of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount of restricted investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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

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