Fair Market Value of Financial Assets and Liabilities, Estimated Fair Value of Financial Instruments and Indication of Level Within Fair Value Hierarchy of Valuation Techniques (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Financial assets [Abstract]
Available-for-sale securities	$ 631,201	$ 594,936
Securities held-to-maturity	1,182	1,651
Mortgage servicing rights	2,964	3,236
Carrying Amount [Member]
Financial assets [Abstract]
Cash and cash equivalents	121,178	187,611
Certificates of deposits in other banks	980	3,832
Available-for-sale securities	631,201	594,936
Securities held-to-maturity	1,181	1,661
Loans held for sale	2,075	1,172
Loans, net	2,895,498	2,837,867
Federal Home Loan Bank stock	17,927	17,927
Federal Reserve Bank stock	4,887	4,887
Accrued interest receivable	11,912	12,194
Mortgage servicing rights	2,964	3,236
Financial liabilities [Abstract]
Deposits	3,053,985	2,980,782
Repurchase agreements	262,295	251,225
Federal funds purchased	6,798	3,596
Advances from Federal Home Loan Bank	971	101,056
Long-term debt	61,341	61,341
Accrued interest payable	2,245	1,071
Unrecognized financial instruments [Abstract]
Letters of credit	0	0
Commitments to extend credit	0	0
Forward sale commitments	0	0
Fair Value [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Financial assets [Abstract]
Cash and cash equivalents	121,178	187,611
Certificates of deposits in other banks	0	0
Available-for-sale securities	70,125	69,453
Securities held-to-maturity	0	0
Loans held for sale	2,119	1,196
Loans, net	0	0
Federal Home Loan Bank stock	0	0
Federal Reserve Bank stock	0	0
Accrued interest receivable	0	0
Mortgage servicing rights	0	0
Financial liabilities [Abstract]
Deposits	763,187	749,975
Repurchase agreements	0	0
Federal funds purchased	0	0
Advances from Federal Home Loan Bank	0	0
Long-term debt	0	0
Accrued interest payable	0	0
Unrecognized financial instruments [Abstract]
Letters of credit	0	0
Commitments to extend credit	0	0
Forward sale commitments	0	0
Fair Value [Member] | Significant Other Observable Inputs (Level 2) [Member]
Financial assets [Abstract]
Cash and cash equivalents	0	0
Certificates of deposits in other banks	983	3,836
Available-for-sale securities	561,076	525,483
Securities held-to-maturity	1,182	1,651
Loans held for sale	0	0
Loans, net	0	0
Federal Home Loan Bank stock	17,927	17,927
Federal Reserve Bank stock	4,887	4,887
Accrued interest receivable	11,912	12,194
Mortgage servicing rights	0	0
Financial liabilities [Abstract]
Deposits	2,299,370	2,208,120
Repurchase agreements	0	0
Federal funds purchased	6,798	3,596
Advances from Federal Home Loan Bank	1,044	100,905
Long-term debt	0	0
Accrued interest payable	2,245	1,071
Unrecognized financial instruments [Abstract]
Letters of credit	0	0
Commitments to extend credit	0	0
Forward sale commitments	0	0
Fair Value [Member] | Significant Unobservable Inputs (Level 3) [Member]
Financial assets [Abstract]
Cash and cash equivalents	0	0
Certificates of deposits in other banks	0	0
Available-for-sale securities	0	0
Securities held-to-maturity	0	0
Loans held for sale	0	0
Loans, net	2,897,616	2,833,267
Federal Home Loan Bank stock	0	0
Federal Reserve Bank stock	0	0
Accrued interest receivable	0	0
Mortgage servicing rights	2,964	3,236
Financial liabilities [Abstract]
Deposits	0	0
Repurchase agreements	262,208	250,873
Federal funds purchased	0	0
Advances from Federal Home Loan Bank	0	0
Long-term debt	49,073	49,073
Accrued interest payable	0	0
Unrecognized financial instruments [Abstract]
Letters of credit	0	0
Commitments to extend credit	0	0
Forward sale commitments	$ 0	$ 0