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, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Financial assets [Abstract]
Securities available-for-sale	$ 640,186us-gaap_AvailableForSaleSecurities	$ 609,405us-gaap_AvailableForSaleSecurities
Securities held-to-maturity	1,644	1,601
Mortgage servicing rights	2,968us-gaap_ServicingAssetAtFairValueAmount	3,424us-gaap_ServicingAssetAtFairValueAmount	2,364us-gaap_ServicingAssetAtFairValueAmount	2,282us-gaap_ServicingAssetAtFairValueAmount
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Financial assets [Abstract]
Cash and cash equivalents	105,517	106,641
Certificates of deposits in other banks	0	0
Securities available-for-sale	24,889	52,782
Securities held-to-maturity	0	0
Loans held for sale	2,321	845
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	677,626	621,321
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
Significant Other Observable Inputs (Level 2) [Member]
Financial assets [Abstract]
Cash and cash equivalents	0	0
Certificates of deposits in other banks	8,213	9,582
Securities available-for-sale	615,297	556,623
Securities held-to-maturity	1,644	1,601
Loans held for sale	0	0
Loans, net	0	0
Federal Home Loan Bank stock	17,927	25,673
Federal Reserve Bank stock	4,869	4,886
Accrued interest receivable	13,548	12,886
Mortgage servicing rights	0	0
Financial liabilities [Abstract]
Deposits	2,192,848	2,230,608
Repurchase agreements	0	0
Federal funds purchased	11,041	12,465
Advances from Federal Home Loan Bank	61,106	1,531
Long-term debt	0	0
Accrued interest payable	908	1,032
Unrecognized financial instruments [Abstract]
Letters of credit	0	0
Commitments to extend credit	0	0
Forward sale commitments	0	0
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	2,691,906	2,589,811
Federal Home Loan Bank stock	0	0
Federal Reserve Bank stock	0	0
Accrued interest receivable	0	0
Mortgage servicing rights	2,968	3,424
Financial liabilities [Abstract]
Deposits	0	0
Repurchase agreements	235,193	207,992
Federal funds purchased	0	0
Advances from Federal Home Loan Bank	0	0
Long-term debt	35,615	31,362
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
Carrying Amount [Member]
Financial assets [Abstract]
Cash and cash equivalents	105,517	106,641
Certificates of deposits in other banks	8,197	9,568
Securities available-for-sale	640,186	609,405
Securities held-to-maturity	1,662	1,662
Loans held for sale	2,264	828
Loans, net	2,699,377	2,581,346
Federal Home Loan Bank stock	17,927	25,673
Federal Reserve Bank stock	4,869	4,886
Accrued interest receivable	13,548	12,886
Mortgage servicing rights	2,968	3,424
Financial liabilities [Abstract]
Deposits	2,874,257	2,855,074
Repurchase agreements	235,186	208,067
Federal funds purchased	11,041	12,465
Advances from Federal Home Loan Bank	61,170	1,286
Long-term debt	61,341	61,341
Accrued interest payable	908	1,032
Unrecognized financial instruments [Abstract]
Letters of credit	0	0
Commitments to extend credit	0	0
Forward sale commitments	$ 0	$ 0

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, unless otherwise specified