Securities - Amortized Cost and Fair Value (Details) $ in Thousands	6 Months Ended
Jun. 30, 2023 USD ($) item	Dec. 31, 2022 USD ($)
Securities Available-for-Sale
Amortized Cost	$ 1,448,010	$ 1,662,819
Gross Unrealized Gains	557	370
Gross Unrealized Losses	(112,945)	(123,830)
Securities available-for-sale	1,335,622	1,539,359
Accrued interest receivable	6,900	6,800
FHLB and FRB Stock
FHLBC stock	21,800	5,600
FRBC stock	14,900	14,900
Securities pledged to secure deposits and for other purposes	938,500	547,800
Other disclosures
Securities available-for-sale	$ 1,335,622	1,539,359
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	$ 224,337	224,054
Gross Unrealized Losses	(9,724)	(11,925)
Securities available-for-sale	214,613	212,129
Other disclosures
Securities available-for-sale	214,613	212,129
U.S. government agencies
Securities Available-for-Sale
Amortized Cost	60,593	61,178
Gross Unrealized Losses	(4,612)	(5,130)
Securities available-for-sale	55,981	56,048
Other disclosures
Securities available-for-sale	55,981	56,048
U.S. government agencies mortgage-backed
Securities Available-for-Sale
Amortized Cost	129,973	140,588
Gross Unrealized Losses	(14,833)	(15,598)
Securities available-for-sale	115,140	124,990
Other disclosures
Securities available-for-sale	115,140	124,990
States and political subdivisions
Securities Available-for-Sale
Amortized Cost	241,764	239,999
Gross Unrealized Gains	557	363
Gross Unrealized Losses	(12,787)	(14,234)
Securities available-for-sale	229,534	226,128
Other disclosures
Securities available-for-sale	229,534	226,128
Corporate bonds
Securities Available-for-Sale
Amortized Cost	5,000	10,000
Gross Unrealized Losses	(118)	(378)
Securities available-for-sale	4,882	9,622
Other disclosures
Securities available-for-sale	4,882	9,622
Collateralized mortgage obligations
Securities Available-for-Sale
Amortized Cost	468,029	596,336
Gross Unrealized Gains		1
Gross Unrealized Losses	(60,534)	(62,569)
Securities available-for-sale	407,495	533,768
Other disclosures
Securities available-for-sale	407,495	533,768
Asset-backed Securities
Securities Available-for-Sale
Amortized Cost	140,791	210,388
Gross Unrealized Gains		6
Gross Unrealized Losses	(6,472)	(8,466)
Securities available-for-sale	134,319	201,928
Other disclosures
Securities available-for-sale	134,319	201,928
Collateralized loan obligations.
Securities Available-for-Sale
Amortized Cost	177,523	180,276
Gross Unrealized Losses	(3,865)	(5,530)
Securities available-for-sale	173,658	174,746
Other disclosures
Securities available-for-sale	$ 173,658	$ 174,746

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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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