Loans & Leases and Allowance for Credit Losses, Loan Portfolio Allocated by Management's Internal Risk Ratings (Details) (USD $)	Jun. 30, 2014	Dec. 31, 2013	Jun. 30, 2013
Financing Receivable, Recorded Investment [Line Items]
Loans & lease	$ 1,499,709,000	$ 1,388,236,000	$ 1,295,056,000
Loans outstanding rated doubtful or loss	0	0	0
Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans & lease	428,529,000	407,514,000	393,159,000
Agricultural Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans & lease	358,933,000	328,264,000	312,588,000
Real Estate Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans & lease	81,647,000	41,092,000	32,718,000
Residential 1st Mortgages [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans & lease	160,418,000	151,292,000	136,473,000
Home Equity Lines & Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans & lease	34,453,000	35,477,000	37,498,000
Agricultural [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans & lease	228,745,000	256,414,000	214,760,000
Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans & lease	179,948,000	150,398,000	159,647,000
Consumer & Other [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans & lease	4,881,000	5,052,000	5,546,000
Leases [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans & lease	22,155,000	12,733,000	2,667,000
Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans & lease	1,461,767,000	1,353,440,000	1,255,088,000
Pass [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans & lease	417,627,000	398,488,000	378,570,000
Pass [Member] | Agricultural Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans & lease	358,933,000	325,926,000	304,516,000
Pass [Member] | Real Estate Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans & lease	80,015,000	39,460,000	26,534,000
Pass [Member] | Residential 1st Mortgages [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans & lease	159,098,000	149,798,000	134,766,000
Pass [Member] | Home Equity Lines & Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans & lease	33,717,000	34,821,000	36,407,000
Pass [Member] | Agricultural [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans & lease	227,891,000	255,443,000	212,923,000
Pass [Member] | Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans & lease	157,709,000	132,008,000	153,445,000
Pass [Member] | Consumer & Other [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans & lease	4,622,000	4,763,000	5,260,000
Pass [Member] | Leases [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans & lease	22,155,000	12,733,000	2,667,000
Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans & lease	34,513,000	29,038,000	23,110,000
Special Mention [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans & lease	10,780,000	7,979,000	7,817,000
Special Mention [Member] | Agricultural Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans & lease	0	2,338,000	1,936,000
Special Mention [Member] | Real Estate Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans & lease	1,632,000	1,632,000	6,184,000
Special Mention [Member] | Residential 1st Mortgages [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans & lease	759,000	774,000	786,000
Special Mention [Member] | Home Equity Lines & Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans & lease	0	0	0
Special Mention [Member] | Agricultural [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans & lease	785,000	889,000	526,000
Special Mention [Member] | Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans & lease	20,557,000	15,426,000	5,861,000
Special Mention [Member] | Consumer & Other [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans & lease	0	0	0
Special Mention [Member] | Leases [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans & lease		0	0
Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans & lease	3,429,000	5,758,000	16,858,000
Substandard [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans & lease	122,000	1,047,000	6,772,000
Substandard [Member] | Agricultural Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans & lease	0	0	6,136,000
Substandard [Member] | Real Estate Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans & lease	0	0	0
Substandard [Member] | Residential 1st Mortgages [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans & lease	561,000	720,000	921,000
Substandard [Member] | Home Equity Lines & Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans & lease	736,000	656,000	1,091,000
Substandard [Member] | Agricultural [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans & lease	69,000	82,000	1,311,000
Substandard [Member] | Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans & lease	1,682,000	2,964,000	341,000
Substandard [Member] | Consumer & Other [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans & lease	259,000	289,000	286,000
Substandard [Member] | Leases [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans & lease	$ 0	$ 0	$ 0