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	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Financial assets [Abstract]
Securities available-for-sale	$ 605,394	$ 594,936
Securities held-to-maturity	867	1,651
Mortgage servicing rights	3,433	3,236	$ 2,968	$ 3,424
Carrying Amount [Member]
Financial assets [Abstract]
Cash and cash equivalents	144,716	187,611
Certificates of deposits in other banks	980	3,832
Securities available-for-sale	605,394	594,936
Securities held-to-maturity	866	1,661
Loans held for sale	1,244	1,172
Loans, net	2,902,438	2,837,867
Federal Home Loan Bank stock	17,927	17,927
Federal Reserve Bank stock	4,887	4,887
Accrued interest receivable	11,922	12,194
Mortgage servicing rights	3,433	3,236
Financial liabilities [Abstract]
Deposits	3,081,308	2,980,782
Repurchase agreements	251,065	251,225
Federal funds purchased	4,816	3,596
Advances from Federal Home Loan Bank	944	101,056
Long-term debt	61,341	61,341
Accrued interest payable	1,200	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	144,716	187,611
Certificates of deposits in other banks	0	0
Securities available-for-sale	69,292	69,453
Securities held-to-maturity	0	0
Loans held for sale	1,260	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	767,918	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	982	3,836
Securities available-for-sale	536,102	525,483
Securities held-to-maturity	867	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	11,922	12,194
Mortgage servicing rights	0	0
Financial liabilities [Abstract]
Deposits	2,321,690	2,208,120
Repurchase agreements	0	0
Federal funds purchased	4,816	3,596
Advances from Federal Home Loan Bank	1,009	100,905
Long-term debt	0	0
Accrued interest payable	1,200	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
Securities available-for-sale	0	0
Securities held-to-maturity	0	0
Loans held for sale	0	0
Loans, net	2,882,348	2,833,267
Federal Home Loan Bank stock	0	0
Federal Reserve Bank stock	0	0
Accrued interest receivable	0	0
Mortgage servicing rights	3,433	3,236
Financial liabilities [Abstract]
Deposits	0	0
Repurchase agreements	250,820	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