Fair Value of Financial Instruments (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012	Jun. 30, 2012
Carrying Amount [Member]
Assets [Abstract]
Cash and Cash Equivalents	$ 45,306	$ 129,426	$ 40,769
Investment Securities Available-for-Sale [Abstract]
Government Agency & Government-Sponsored Entities	26,482	26,823	57,078
Obligations of States and Political Subdivisions	5,612	5,665	5,724
Mortgage Backed Securities	392,574	352,772	427,637
Corporate Securities	49,560	22,558	8,995
Other	1,186	10,173	2,458
Total Assets Measured at Fair Value On a Recurring Basis	475,414	417,991	501,892
Investment Securities Held-to-Maturity [Abstract]
Obligations of States and Political Subdivisions	64,648	65,694	67,159
Mortgage Backed Securities	217	484	806
Other	2,194	2,214	2,230
Total Investment Securities Held-to-Maturity	67,059	68,392	70,195
FHLB Stock	7,187	7,368	7,368
Loans & Leases, Net of Deferred Fees & Allowance [Abstract]
Commercial Real Estate	387,427	344,084	320,418
Agricultural Real Estate	309,107	309,115	282,997
Real Estate Construction	31,741	31,694	34,133
Residential 1st Mortgages	135,436	139,038	121,602
Home Equity Lines and Loans	34,514	38,807	42,770
Agricultural	204,203	210,595	202,946
Commercial	150,572	135,330	162,083
Consumer & Other	5,378	4,876	5,658
Leases	2,667
Unallocated Allowance	(224)	(854)	(1,711)
Total Loans & Leases, Net of Deferred Fees & Allowance	1,260,821	1,212,685	1,170,896
Accrued Interest Receivable	7,609	6,389	7,223
Deposits [Abstract]
Demand	429,526	462,251	360,290
Interest Bearing Transaction	248,447	259,141	223,343
Savings and Money Market	588,009	541,526	542,922
Time	444,175	459,108	505,670
Total Deposits	1,710,157	1,722,026	1,632,225
FHLB Advances & Securities Sold Under Agreement to Repurchase	43,300		50,998
Subordinated Debentures	10,310	10,310	10,310
Accrued Interest Payable	438	498	796
Estimated Fair Value [Member]
Assets [Abstract]
Cash and Cash Equivalents	45,306	129,426	40,769
Investment Securities Available-for-Sale [Abstract]
Government Agency & Government-Sponsored Entities	26,482	26,823	57,078
Obligations of States and Political Subdivisions	5,612	5,665	5,724
Mortgage Backed Securities	392,574	352,772	427,637
Corporate Securities	49,560	22,558	8,995
Other	1,186	10,173	2,458
Total Assets Measured at Fair Value On a Recurring Basis	475,414	417,991	501,892
Investment Securities Held-to-Maturity [Abstract]
Obligations of States and Political Subdivisions	65,369	67,987	69,606
Mortgage Backed Securities	220	496	831
Other	2,194	2,214	2,230
Total Investment Securities Held-to-Maturity	67,783	70,697	72,667
Loans & Leases, Net of Deferred Fees & Allowance [Abstract]
Commercial Real Estate	387,017	349,524	330,783
Agricultural Real Estate	310,902	316,302	292,152
Real Estate Construction	31,901	32,024	34,423
Residential 1st Mortgages	137,951	144,203	125,110
Home Equity Lines and Loans	37,225	41,419	45,809
Agricultural	201,957	209,578	202,991
Commercial	149,593	134,647	161,242
Consumer & Other	5,400	4,847	5,731
Leases	2,667
Unallocated Allowance	(224)	(854)	(1,711)
Total Loans & Leases, Net of Deferred Fees & Allowance	1,264,389	1,231,690	1,196,530
Accrued Interest Receivable	7,609	6,389	7,223
Deposits [Abstract]
Demand	429,526	462,251	360,290
Interest Bearing Transaction	248,447	259,141	223,343
Savings and Money Market	588,009	541,526	542,922
Time	444,579	459,993	506,638
Total Deposits	1,710,561	1,722,911	1,633,193
FHLB Advances & Securities Sold Under Agreement to Repurchase	43,300		51,065
Subordinated Debentures	5,665	5,750	5,841
Accrued Interest Payable	438	498	796
Estimated Fair Value [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Assets [Abstract]
Cash and Cash Equivalents	45,306	129,426	40,769
Investment Securities Available-for-Sale [Abstract]
Government Agency & Government-Sponsored Entities	21,416	21,731	10,724
Obligations of States and Political Subdivisions	0	0	0
Mortgage Backed Securities		0	0
Corporate Securities	8,122	4,020	0
Other	876	9,863	2,148
Total Assets Measured at Fair Value On a Recurring Basis	30,414	35,614	12,872
Investment Securities Held-to-Maturity [Abstract]
Obligations of States and Political Subdivisions	0	0	0
Mortgage Backed Securities	0	0	0
Other	0	0	0
Total Investment Securities Held-to-Maturity	0	0	0
Loans & Leases, Net of Deferred Fees & Allowance [Abstract]
Commercial Real Estate	0	0	0
Agricultural Real Estate	0	0	0
Real Estate Construction	0	0	0
Residential 1st Mortgages	0	0	0
Home Equity Lines and Loans	0	0	0
Agricultural	0	0	0
Commercial	0	0	0
Consumer & Other	0	0	0
Leases	0
Unallocated Allowance	0	0	0
Total Loans & Leases, Net of Deferred Fees & Allowance	0	0	0
Accrued Interest Receivable	0	0	0
Deposits [Abstract]
Demand	429,526	462,251	360,290
Interest Bearing Transaction	248,447	259,141	223,343
Savings and Money Market	588,009	541,526	542,922
Time	0	0	0
Total Deposits	1,265,982	1,262,918	1,126,555
FHLB Advances & Securities Sold Under Agreement to Repurchase	0		0
Subordinated Debentures	0	0	0
Accrued Interest Payable	0	0	0
Estimated Fair Value [Member] | Other Observable Inputs (Level 2) [Member]
Assets [Abstract]
Cash and Cash Equivalents	0	0	0
Investment Securities Available-for-Sale [Abstract]
Government Agency & Government-Sponsored Entities	5,066	5,092	46,354
Obligations of States and Political Subdivisions	0	0	0
Mortgage Backed Securities	392,574	352,772	427,637
Corporate Securities	41,438	18,538	8,995
Other	310	310	310
Total Assets Measured at Fair Value On a Recurring Basis	439,388	376,712	483,296
Investment Securities Held-to-Maturity [Abstract]
Obligations of States and Political Subdivisions	58,009	60,177	61,820
Mortgage Backed Securities	220	496	831
Other	2,194	2,214	2,230
Total Investment Securities Held-to-Maturity	60,423	62,887	64,881
Loans & Leases, Net of Deferred Fees & Allowance [Abstract]
Commercial Real Estate	0	0	0
Agricultural Real Estate	0	0	0
Real Estate Construction	0	0	0
Residential 1st Mortgages	0	0	0
Home Equity Lines and Loans	0	0	0
Agricultural	0	0	0
Commercial	0	0	0
Consumer & Other	0	0	0
Leases	0
Unallocated Allowance	0	0	0
Total Loans & Leases, Net of Deferred Fees & Allowance	0	0	0
Accrued Interest Receivable	7,609	0	7,223
Deposits [Abstract]
Demand	0	0	0
Interest Bearing Transaction	0	0	0
Savings and Money Market	0	0	0
Time	444,579	459,993	506,638
Total Deposits	444,579	459,993	506,638
FHLB Advances & Securities Sold Under Agreement to Repurchase	43,300		51,065
Subordinated Debentures	5,665	5,750	5,841
Accrued Interest Payable	438	498	796
Estimated Fair Value [Member] | Significant Unobservable Inputs (Level 3) [Member]
Assets [Abstract]
Cash and Cash Equivalents	0	0	0
Investment Securities Available-for-Sale [Abstract]
Government Agency & Government-Sponsored Entities	0	0	0
Obligations of States and Political Subdivisions	5,612	5,665	5,724
Mortgage Backed Securities	0	0	0
Corporate Securities	0	0	0
Other	0	0	0
Total Assets Measured at Fair Value On a Recurring Basis	5,612	5,665	5,724
Investment Securities Held-to-Maturity [Abstract]
Obligations of States and Political Subdivisions	7,360	7,810	7,786
Mortgage Backed Securities	0	0	0
Other	0	0	0
Total Investment Securities Held-to-Maturity	7,360	7,810	7,786
Loans & Leases, Net of Deferred Fees & Allowance [Abstract]
Commercial Real Estate	387,017	349,524	330,783
Agricultural Real Estate	310,902	316,302	292,152
Real Estate Construction	31,901	32,024	34,423
Residential 1st Mortgages	137,951	144,203	125,110
Home Equity Lines and Loans	37,225	41,419	45,809
Agricultural	201,957	209,578	202,991
Commercial	149,593	134,647	161,242
Consumer & Other	5,400	4,847	5,731
Leases	2,667
Unallocated Allowance	(224)	(854)	(1,711)
Total Loans & Leases, Net of Deferred Fees & Allowance	1,264,389	1,231,690	1,196,530
Accrued Interest Receivable	0	6,389	0
Deposits [Abstract]
Demand	0	0	0
Interest Bearing Transaction	0	0	0
Savings and Money Market	0	0	0
Time	0	0	0
Total Deposits	0	0	0
FHLB Advances & Securities Sold Under Agreement to Repurchase	0		0
Subordinated Debentures	0	0	0
Accrued Interest Payable	$ 0	$ 0	$ 0