Fair Values of Financial Instruments (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Financial assets:
Cash and due from banks	$ 32,614	$ 33,805
Interest bearing deposits with financial institutions	18,483	13,529
Securities available-for-sale	568,227	531,838
FHLBC and FRBC Stock	8,593	7,918
Bank-owned life insurance	61,041	60,332
Financial liabilities:
Noninterest bearing deposits	546,463	513,688
Other short-term borrowings	75,000	70,000
Junior subordinated debentures	57,615	57,591
Carrying Amount
Financial assets:
Cash and due from banks	32,614	33,805
Interest bearing deposits with financial institutions	18,483	13,529
Securities available-for-sale	568,227	531,838
FHLBC and FRBC Stock	8,593	7,918
Loans held for sale	5,440	4,918
Loans, net	1,523,811	1,462,651
Accrued interest receivable	7,569	5,928
Financial liabilities:
Noninterest bearing deposits	546,463	513,688
Interest bearing deposits	1,363,682	1,353,097
Securities sold under repurchase agreements	36,361	25,715
Other short-term borrowings	75,000	70,000
Junior subordinated debentures	57,615	57,591
Subordinated debenture	44,008	43,998
Interest rate swap	1,458	994
Borrowing interest payable	89	202
Deposit interest payable	611	599
Total Fair Value
Financial assets:
Cash and due from banks	32,614	33,805
Interest bearing deposits with financial institutions	18,483	13,529
Securities available-for-sale	568,227	531,838
FHLBC and FRBC Stock	8,593	7,918
Loans held for sale	5,440	4,918
Loans, net	1,519,216	1,453,429
Accrued interest receivable	7,569	5,928
Financial liabilities:
Noninterest bearing deposits	546,463	513,688
Interest bearing deposits	1,375,085	1,351,000
Securities sold under repurchase agreements	36,361	25,715
Other short-term borrowings	75,000	70,000
Junior subordinated debentures	60,534	55,163
Subordinated debenture	46,258	43,998
Interest rate swap	1,458	994
Borrowing interest payable	89	202
Deposit interest payable	611	599
Level 1
Financial assets:
Cash and due from banks	32,614	33,805
Interest bearing deposits with financial institutions	18,483	13,529
Financial liabilities:
Noninterest bearing deposits	546,463	513,688
Junior subordinated debentures	33,472	32,404
Level 2
Financial assets:
Securities available-for-sale	545,201	506,493
FHLBC and FRBC Stock	8,593	7,918
Loans held for sale	5,440	4,918
Accrued interest receivable	7,569	5,928
Financial liabilities:
Interest bearing deposits	1,375,085	1,351,000
Securities sold under repurchase agreements	36,361	25,715
Other short-term borrowings	75,000	70,000
Junior subordinated debentures	27,062	22,759
Subordinated debenture	46,258	43,998
Interest rate swap	1,458	994
Borrowing interest payable	89	202
Deposit interest payable	611	599
Level 3
Financial assets:
Securities available-for-sale	23,026	25,345
Loans, net	$ 1,519,216	$ 1,453,429