Securities - Amortized Cost and Fair Value (Details) $ in Thousands	12 Months Ended
Dec. 31, 2023 USD ($) item	Dec. 31, 2022 USD ($)
Securities Available-for-Sale
Amortized Cost	$ 1,276,981	$ 1,662,819
Gross Unrealized Gains	1,818	370
Gross Unrealized Losses	(85,970)	(123,830)
Securities available-for-sale	1,192,829	1,539,359
Accrued interest receivable	6,600	6,800
FHLB and FRB Stock
FHLBC stock	18,500	5,600
FRBC stock	14,900	14,900
Securities pledged to secure deposits and for other purposes	810,200	547,800
Other disclosures
Securities available-for-sale	$ 1,192,829	1,539,359
Number of securities issued from originators	0
Number of originators \| item	1
Minimum percentage of securities investment	10.00%
US government and agencies debt securities, percentage of guarantee	100.00%
US government and agencies debt securities, threshold percentage of guarantee for allowance of credit loss	100.00%
U.S. Treasury
Securities Available-for-Sale
Amortized Cost	$ 174,602	224,054
Gross Unrealized Losses	(5,028)	(11,925)
Securities available-for-sale	169,574	212,129
Other disclosures
Securities available-for-sale	169,574	212,129
U.S. government agencies
Securities Available-for-Sale
Amortized Cost	60,011	61,178
Gross Unrealized Losses	(3,052)	(5,130)
Securities available-for-sale	56,959	56,048
Other disclosures
Securities available-for-sale	56,959	56,048
U.S. government agencies mortgage-backed
Securities Available-for-Sale
Amortized Cost	118,492	140,588
Gross Unrealized Losses	(12,122)	(15,598)
Securities available-for-sale	106,370	124,990
Other disclosures
Securities available-for-sale	106,370	124,990
States and political subdivisions
Securities Available-for-Sale
Amortized Cost	238,440	239,999
Gross Unrealized Gains	1,325	363
Gross Unrealized Losses	(10,430)	(14,234)
Securities available-for-sale	229,335	226,128
Other disclosures
Securities available-for-sale	229,335	226,128
Corporate bonds
Securities Available-for-Sale
Amortized Cost		10,000
Gross Unrealized Losses		(378)
Securities available-for-sale		9,622
Other disclosures
Securities available-for-sale		9,622
Collateralized mortgage obligations
Securities Available-for-Sale
Amortized Cost	442,987	596,336
Gross Unrealized Gains	421	1
Gross Unrealized Losses	(50,864)	(62,569)
Securities available-for-sale	392,544	533,768
Other disclosures
Securities available-for-sale	392,544	533,768
Asset-backed Securities
Securities Available-for-Sale
Amortized Cost	69,248	210,388
Gross Unrealized Gains	42	6
Gross Unrealized Losses	(3,124)	(8,466)
Securities available-for-sale	66,166	201,928
Other disclosures
Securities available-for-sale	66,166	201,928
Collateralized loan obligations.
Securities Available-for-Sale
Amortized Cost	173,201	180,276
Gross Unrealized Gains	30
Gross Unrealized Losses	(1,350)	(5,530)
Securities available-for-sale	171,881	174,746
Other disclosures
Securities available-for-sale	$ 171,881	$ 174,746
Minimum
Other disclosures
Debt securities, available-for-sale, allowance for credit loss, percent of market value loss	5.00%
Debt securities, available-for-sale, allowance for credit loss, market value loss	$ 200,000

The market value loss of debt securities available for sale, for evaluation of allowance for credit loss.

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The market value loss of debt securities available for sale, as percent of book value for evaluation of allowance for credit loss.

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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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The percentage of guarantee by Us government and agencies.

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The threshold percentage of guarantee by Us government and agencies for allowance of credit loss.

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- Definition

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

+ References

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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).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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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).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
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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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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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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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