Fair Value Measurements (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012
Other Real Estate [Abstract]
Impaired loans with a partial charge-off or where an allowance was established	$ 2,500,000	$ 560,000	$ 2,500,000	$ 560,000	$ 1,700,000
ORE, valuation allowance	3,700,000	4,100,000	3,700,000	4,100,000	4,100,000
Allowance for credit losses	1,300,000	915,000	1,300,000	915,000	1,400,000
Recurring [Member]
Available-for-Sale Securities [Abstract]
Government Agency & Government-Sponsored Entities	26,482,000	57,078,000	26,482,000	57,078,000	26,823,000
Obligations of States and Political Subdivisions	5,612,000	5,724,000	5,612,000	5,724,000	5,665,000
Mortgage Backed Securities	392,574,000	427,637,000	392,574,000	427,637,000	352,772,000
Corporate Securities	49,560,000	8,995,000	49,560,000	8,995,000	22,558,000
Other	1,186,000	2,458,000	1,186,000	2,458,000	10,173,000
Total Assets Measured at Fair Value On a Recurring Basis	475,414,000	501,892,000	475,414,000	501,892,000	417,991,000
Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Available-for-Sale Securities [Abstract]
Government Agency & Government-Sponsored Entities	21,416,000	10,724,000	21,416,000	10,724,000	21,731,000
Obligations of States and Political Subdivisions	0	0	0	0	0
Mortgage Backed Securities	0	0	0	0	0
Corporate Securities	8,122,000	0	8,122,000	0	4,020,000
Other	876,000	2,148,000	876,000	2,148,000	9,863,000
Total Assets Measured at Fair Value On a Recurring Basis	30,414,000	12,872,000	30,414,000	12,872,000	35,614,000
Recurring [Member] | Other Observable Inputs (Level 2) [Member]
Available-for-Sale Securities [Abstract]
Government Agency & Government-Sponsored Entities	5,066,000	46,354,000	5,066,000	46,354,000	5,092,000
Obligations of States and Political Subdivisions	0	0	0	0	0
Mortgage Backed Securities	392,574,000	427,637,000	392,574,000	427,637,000	352,772,000
Corporate Securities	41,438,000	8,995,000	41,438,000	8,995,000	18,538,000
Other	310,000	310,000	310,000	310,000	310,000
Total Assets Measured at Fair Value On a Recurring Basis	439,388,000	483,296,000	439,388,000	483,296,000	376,712,000
Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member]
Available-for-Sale Securities [Abstract]
Government Agency & Government-Sponsored Entities	0	0	0	0	0
Obligations of States and Political Subdivisions	5,612,000	5,724,000	5,612,000	5,724,000	5,665,000
Mortgage Backed Securities	0	0	0	0	0
Corporate Securities	0	0	0	0	0
Other	0	0	0	0	0
Total Assets Measured at Fair Value On a Recurring Basis	5,612,000	5,724,000	5,612,000	5,724,000	5,665,000
Changes in level 3 assets measured at fair value on a recurring basis [Roll Forward]
Balance at Beginning of Period	5,643,000	5,753,000	5,665,000	5,782,000
Total Realized and Unrealized Gains/(Losses) Included in Income	0	0	0	0
Total Unrealized Gains/(Losses) Included in Other Comprehensive Income	0	0	0	0
Purchase of Securities	0	0	0	0
Sales, Maturities, and Calls of Securities	(31,000)	(29,000)	(53,000)	(58,000)
Net Transfers In/(Out) of Level 3	0	0	0	0
Balance at End of Period	5,612,000	5,724,000	5,612,000	5,724,000
Nonrecurring [Member]
Impaired Loans [Abstract]
Agricultural Real Estate	1,143,000		1,143,000
Residential 1st Mortgage	283,000	86,000	283,000	86,000	235,000
Home Equity Lines and Loans	184,000	428,000	184,000	428,000	462,000
Agricultural	672,000		672,000		1,010,000
Commercial	216,000	48,000	216,000	48,000
Total Impaired Loans	2,498,000	562,000	2,498,000	562,000	1,707,000
Other Real Estate [Abstract]
Real Estate Construction	2,399,000	2,553,000	2,399,000	2,553,000	2,553,000
Total Other Real Estate	2,399,000	2,553,000	2,399,000	2,553,000	2,553,000
Total Assets Measured at Fair Value On a Non-Recurring Basis	4,897,000	3,115,000	4,897,000	3,115,000	4,260,000
Nonrecurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Impaired Loans [Abstract]
Agricultural Real Estate	0		0
Residential 1st Mortgage	0	0	0	0	0
Home Equity Lines and Loans	0	0	0	0	0
Agricultural	0		0		0
Commercial	0	0	0	0
Total Impaired Loans	0	0	0	0	0
Other Real Estate [Abstract]
Real Estate Construction	0	0	0	0	0
Total Other Real Estate	0	0	0	0	0
Total Assets Measured at Fair Value On a Non-Recurring Basis	0	0	0	0	0
Nonrecurring [Member] | Other Observable Inputs (Level 2) [Member]
Impaired Loans [Abstract]
Agricultural Real Estate	0		0
Residential 1st Mortgage	0	0	0	0	0
Home Equity Lines and Loans	0	0	0	0	0
Agricultural	0		0		0
Commercial	0	0	0	0
Total Impaired Loans	0	0	0	0	0
Other Real Estate [Abstract]
Real Estate Construction	0	0	0	0	0
Total Other Real Estate	0	0	0	0	0
Total Assets Measured at Fair Value On a Non-Recurring Basis	0	0	0	0	0
Nonrecurring [Member] | Significant Unobservable Inputs (Level 3) [Member]
Impaired Loans [Abstract]
Agricultural Real Estate	1,143,000		1,143,000
Residential 1st Mortgage	283,000	86,000	283,000	86,000	235,000
Home Equity Lines and Loans	184,000	428,000	184,000	428,000	462,000
Agricultural	672,000		672,000		1,010,000
Commercial	216,000	48,000	216,000	48,000
Total Impaired Loans	2,498,000	562,000	2,498,000	562,000	1,707,000
Other Real Estate [Abstract]
Real Estate Construction	2,399,000	2,553,000	2,399,000	2,553,000	2,553,000
Total Other Real Estate	2,399,000	2,553,000	2,399,000	2,553,000	2,553,000
Total Assets Measured at Fair Value On a Non-Recurring Basis	$ 4,897,000	$ 3,115,000	$ 4,897,000	$ 3,115,000	$ 4,260,000