Fair Values of Financial Instruments (Details) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Financial assets:
Cash and due from banks	$ 53,295	$ 38,565
Interest earning deposits with financial institutions	228,040	713,542
Securities available-for-sale	1,734,416	1,693,632
FHLBC and FRBC Stock	20,413	13,257
Mortgage servicing rights	10,722	7,097
Financial liabilities:
Noninterest bearing deposits	2,078,272	2,093,494
Junior subordinated debentures	25,773	25,773
Senior notes	44,533	44,480
Reported Value Measurement [Member]
Financial assets:
Cash and due from banks	53,295	38,565
Interest earning deposits with financial institutions	228,040	713,542
Securities available-for-sale	1,734,416	1,693,632
FHLBC and FRBC Stock	20,413	13,257
Loans held for sale	1,707	4,737
Credit card portfolio, reported in other assets	4,956
Net loans	3,579,682	3,376,523
Mortgage servicing rights	10,722	7,097
Interest rate swap agreements	2,770	3,494
Interests rate lock commitments and forward contracts	153	508
Interest receivable on securities and loans	16,495	13,431
Financial liabilities:
Noninterest bearing deposits	2,078,272	2,093,494
Interest bearing deposits	3,264,583	3,372,738
Securities sold under repurchase agreements	37,599	50,377
Junior subordinated debentures	25,773	25,773
Subordinated debentures	59,254	59,212
Senior notes	44,533	44,480
Note payable and other borrowings	11,000	19,074
Interest rate swap agreements	3,576	6,788
Interest payable on deposits and borrowings	1,359	1,706
Estimate of Fair Value Measurement [Member]
Financial assets:
Cash and due from banks	53,295	38,565
Interest earning deposits with financial institutions	228,040	713,542
Securities available-for-sale	1,734,416	1,693,632
FHLBC and FRBC Stock	20,413	13,257
Loans held for sale	1,707	4,737
Credit card portfolio, reported in other assets	4,956
Net loans	3,491,324	3,407,596
Mortgage servicing rights	10,722	7,097
Interest rate swap agreements	2,770	3,494
Interests rate lock commitments and forward contracts	153	508
Interest receivable on securities and loans	16,495	13,431
Financial liabilities:
Noninterest bearing deposits	2,078,272	2,093,494
Interest bearing deposits	3,254,995	3,375,930
Securities sold under repurchase agreements	37,599	50,377
Junior subordinated debentures	22,938	18,557
Subordinated debentures	55,054	60,111
Senior notes	44,465	44,480
Note payable and other borrowings	10,950	19,411
Interest rate swap agreements	3,576	6,788
Interest payable on deposits and borrowings	1,359	1,706
Fair Value, Inputs, Level 1 [Member]
Financial assets:
Cash and due from banks	53,295	38,565
Interest earning deposits with financial institutions	228,040	713,542
Securities available-for-sale	214,820	202,339
Financial liabilities:
Noninterest bearing deposits	2,078,272	2,093,494
Senior notes	44,465	44,480
Fair Value, Inputs, Level 2 [Member]
Financial assets:
Securities available-for-sale	1,506,508	1,476,057
FHLBC and FRBC Stock	20,413	13,257
Loans held for sale	1,707	4,737
Credit card portfolio, reported in other assets	4,956
Interest rate swap agreements	2,770	3,494
Interests rate lock commitments and forward contracts	153	508
Interest receivable on securities and loans	16,495	13,431
Financial liabilities:
Interest bearing deposits	3,254,995	3,375,930
Securities sold under repurchase agreements	37,599	50,377
Junior subordinated debentures	22,938	18,557
Subordinated debentures	55,054	60,111
Note payable and other borrowings	10,950	19,411
Interest rate swap agreements	3,576	6,788
Interest payable on deposits and borrowings	1,359	1,706
Fair Value, Inputs, Level 3 [Member]
Financial assets:
Securities available-for-sale	13,088	15,236
Net loans	3,491,324	3,407,596
Mortgage servicing rights	$ 10,722	$ 7,097