Fair Values of Financial Instruments (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Financial assets:
Cash and due from banks	$ 29,489	$ 34,096
Interest bearing deposits with financial institutions	283,651	16,536
Securities available-for-sale	448,421	484,648
FHLBC and FRBC Stock	9,917	9,917
Bank-owned life insurance	62,222	61,763
Financial liabilities:
Noninterest bearing deposits	889,085	669,795
Other short-term borrowings	6,125	48,500
Junior subordinated debentures	25,773	57,734
Reported Value Measurement [Member]
Financial assets:
Cash and due from banks	29,489	34,096
Interest bearing deposits with financial institutions	283,651	16,536
Securities available-for-sale	448,421	484,648
FHLBC and FRBC Stock	9,917	9,917
Loans held for sale	10,229	3,061
Net loans	1,997,409	1,911,023
Interest rate swap agreements	10,506	2,771
Accrued interest receivable	9,706	9,697
Financial liabilities:
Noninterest bearing deposits	889,085	669,795
Interest bearing deposits	1,590,158	1,456,954
Securities sold under repurchase agreements	59,268	48,693
Other short-term borrowings	6,125	48,500
Junior subordinated debentures	25,773	57,734
Senior notes	44,349	44,270
Note payable and other borrowings	24,469	6,673
Interest rate swap	15,128	5,921
Borrowing interest payable	1,257	1,079
Estimate of Fair Value Measurement [Member]
Financial assets:
Cash and due from banks	29,489	34,096
Interest bearing deposits with financial institutions	283,651	16,536
Securities available-for-sale	448,421	484,648
FHLBC and FRBC Stock	9,917	9,917
Loans held for sale	10,229	3,061
Net loans	2,013,415	1,915,531
Interest rate swap agreements	10,506	2,771
Accrued interest receivable	9,706	9,697
Financial liabilities:
Noninterest bearing deposits	889,085	669,795
Interest bearing deposits	1,593,058	1,457,832
Securities sold under repurchase agreements	59,268	48,693
Other short-term borrowings	6,125	48,500
Junior subordinated debentures	14,167	51,188
Senior notes	44,799	46,269
Note payable and other borrowings	25,160	7,003
Interest rate swap	15,128	5,921
Borrowing interest payable	1,257	1,079
Fair Value, Inputs, Level 1 [Member]
Financial assets:
Cash and due from banks	29,489	34,096
Interest bearing deposits with financial institutions	283,651	16,536
Securities available-for-sale	4,134	4,036
Financial liabilities:
Noninterest bearing deposits	889,085	669,795
Junior subordinated debentures		33,614
Senior notes	44,799	46,269
Fair Value, Inputs, Level 2 [Member]
Financial assets:
Securities available-for-sale	439,497	475,193
FHLBC and FRBC Stock	9,917	9,917
Loans held for sale	10,229	3,061
Interest rate swap agreements	10,506	2,771
Accrued interest receivable	9,706	9,697
Financial liabilities:
Interest bearing deposits	1,593,058	1,457,832
Securities sold under repurchase agreements	59,268	48,693
Other short-term borrowings	6,125	48,500
Junior subordinated debentures	14,167	17,574
Note payable and other borrowings	25,160	7,003
Interest rate swap	15,128	5,921
Borrowing interest payable	1,257	1,079
Level 3
Financial assets:
Securities available-for-sale	4,790	5,419
Net loans	$ 2,013,415	$ 1,915,531