Loans, Credit Quality Indicator (Details) (USD $)			3 Months Ended
	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2013 Minimum [Member]	Mar. 31, 2013 Maximum [Member]	Mar. 31, 2013 Real Estate Loans [Member] Mortgages [Member]	Dec. 31, 2012 Real Estate Loans [Member] Mortgages [Member]	Mar. 31, 2013 Real Estate Loans [Member] Home Equity [Member]	Dec. 31, 2012 Real Estate Loans [Member] Home Equity [Member]	Mar. 31, 2013 Real Estate Loans [Member] Commercial [Member]	Dec. 31, 2012 Real Estate Loans [Member] Commercial [Member]	Mar. 31, 2013 Real Estate Loans [Member] Agricultural [Member]	Dec. 31, 2012 Real Estate Loans [Member] Agricultural [Member]	Mar. 31, 2013 Real Estate Loans [Member] Construction [Member]	Dec. 31, 2012 Real Estate Loans [Member] Construction [Member]	Mar. 31, 2013 Consumer [Member]	Dec. 31, 2012 Consumer [Member]	Mar. 31, 2013 Other Commercial Loans [Member]	Dec. 31, 2012 Other Commercial Loans [Member]	Mar. 31, 2013 Other Agricultural Loans [Member]	Dec. 31, 2012 Other Agricultural Loans [Member]	Mar. 31, 2013 State and Political Subdivision Loans [Member]	Dec. 31, 2012 State and Political Subdivision Loans [Member]	Mar. 31, 2013 Pass [Member]	Dec. 31, 2012 Pass [Member]	Mar. 31, 2013 Pass [Member] Real Estate Loans [Member] Commercial [Member]	Dec. 31, 2012 Pass [Member] Real Estate Loans [Member] Commercial [Member]	Mar. 31, 2013 Pass [Member] Real Estate Loans [Member] Agricultural [Member]	Dec. 31, 2012 Pass [Member] Real Estate Loans [Member] Agricultural [Member]	Mar. 31, 2013 Pass [Member] Real Estate Loans [Member] Construction [Member]	Dec. 31, 2012 Pass [Member] Real Estate Loans [Member] Construction [Member]	Mar. 31, 2013 Pass [Member] Other Commercial Loans [Member]	Dec. 31, 2012 Pass [Member] Other Commercial Loans [Member]	Mar. 31, 2013 Pass [Member] Other Agricultural Loans [Member]	Dec. 31, 2012 Pass [Member] Other Agricultural Loans [Member]	Mar. 31, 2013 Pass [Member] State and Political Subdivision Loans [Member]	Dec. 31, 2012 Pass [Member] State and Political Subdivision Loans [Member]	Mar. 31, 2013 Special Mention [Member]	Dec. 31, 2012 Special Mention [Member]	Mar. 31, 2013 Special Mention [Member] Real Estate Loans [Member] Commercial [Member]	Dec. 31, 2012 Special Mention [Member] Real Estate Loans [Member] Commercial [Member]	Mar. 31, 2013 Special Mention [Member] Real Estate Loans [Member] Agricultural [Member]	Dec. 31, 2012 Special Mention [Member] Real Estate Loans [Member] Agricultural [Member]	Mar. 31, 2013 Special Mention [Member] Real Estate Loans [Member] Construction [Member]	Dec. 31, 2012 Special Mention [Member] Real Estate Loans [Member] Construction [Member]	Mar. 31, 2013 Special Mention [Member] Other Commercial Loans [Member]	Dec. 31, 2012 Special Mention [Member] Other Commercial Loans [Member]	Mar. 31, 2013 Special Mention [Member] Other Agricultural Loans [Member]	Dec. 31, 2012 Special Mention [Member] Other Agricultural Loans [Member]	Mar. 31, 2013 Special Mention [Member] State and Political Subdivision Loans [Member]	Dec. 31, 2012 Special Mention [Member] State and Political Subdivision Loans [Member]	Mar. 31, 2013 Substandard [Member]	Dec. 31, 2012 Substandard [Member]	Mar. 31, 2013 Substandard [Member] Real Estate Loans [Member] Commercial [Member]	Dec. 31, 2012 Substandard [Member] Real Estate Loans [Member] Commercial [Member]	Mar. 31, 2013 Substandard [Member] Real Estate Loans [Member] Agricultural [Member]	Dec. 31, 2012 Substandard [Member] Real Estate Loans [Member] Agricultural [Member]	Mar. 31, 2013 Substandard [Member] Real Estate Loans [Member] Construction [Member]	Dec. 31, 2012 Substandard [Member] Real Estate Loans [Member] Construction [Member]	Mar. 31, 2013 Substandard [Member] Other Commercial Loans [Member]	Dec. 31, 2012 Substandard [Member] Other Commercial Loans [Member]	Mar. 31, 2013 Substandard [Member] Other Agricultural Loans [Member]	Dec. 31, 2012 Substandard [Member] Other Agricultural Loans [Member]	Mar. 31, 2013 Substandard [Member] State and Political Subdivision Loans [Member]	Dec. 31, 2012 Substandard [Member] State and Political Subdivision Loans [Member]	Mar. 31, 2013 Doubtful [Member]	Dec. 31, 2012 Doubtful [Member]	Mar. 31, 2013 Doubtful [Member] Real Estate Loans [Member] Commercial [Member]	Dec. 31, 2012 Doubtful [Member] Real Estate Loans [Member] Commercial [Member]	Mar. 31, 2013 Doubtful [Member] Real Estate Loans [Member] Agricultural [Member]	Dec. 31, 2012 Doubtful [Member] Real Estate Loans [Member] Agricultural [Member]	Mar. 31, 2013 Doubtful [Member] Real Estate Loans [Member] Construction [Member]	Dec. 31, 2012 Doubtful [Member] Real Estate Loans [Member] Construction [Member]	Mar. 31, 2013 Doubtful [Member] Other Commercial Loans [Member]	Dec. 31, 2012 Doubtful [Member] Other Commercial Loans [Member]	Mar. 31, 2013 Doubtful [Member] Other Agricultural Loans [Member]	Dec. 31, 2012 Doubtful [Member] Other Agricultural Loans [Member]	Mar. 31, 2013 Doubtful [Member] State and Political Subdivision Loans [Member]	Dec. 31, 2012 Doubtful [Member] State and Political Subdivision Loans [Member]	Mar. 31, 2013 Loss [Member]	Dec. 31, 2012 Loss [Member]	Mar. 31, 2013 Loss [Member] Real Estate Loans [Member] Commercial [Member]	Dec. 31, 2012 Loss [Member] Real Estate Loans [Member] Commercial [Member]	Mar. 31, 2013 Loss [Member] Real Estate Loans [Member] Agricultural [Member]	Dec. 31, 2012 Loss [Member] Real Estate Loans [Member] Agricultural [Member]	Mar. 31, 2013 Loss [Member] Real Estate Loans [Member] Construction [Member]	Dec. 31, 2012 Loss [Member] Real Estate Loans [Member] Construction [Member]	Mar. 31, 2013 Loss [Member] Other Commercial Loans [Member]	Dec. 31, 2012 Loss [Member] Other Commercial Loans [Member]	Mar. 31, 2013 Loss [Member] Other Agricultural Loans [Member]	Dec. 31, 2012 Loss [Member] Other Agricultural Loans [Member]	Mar. 31, 2013 Loss [Member] State and Political Subdivision Loans [Member]	Dec. 31, 2012 Loss [Member] State and Political Subdivision Loans [Member]	Mar. 31, 2013 Internally Assigned Grade [Member]	Dec. 31, 2012 Internally Assigned Grade [Member]	Mar. 31, 2013 Performing [Member]	Dec. 31, 2012 Performing [Member]	Mar. 31, 2013 Performing [Member] Real Estate Loans [Member] Mortgages [Member]	Dec. 31, 2012 Performing [Member] Real Estate Loans [Member] Mortgages [Member]	Mar. 31, 2013 Performing [Member] Real Estate Loans [Member] Home Equity [Member]	Dec. 31, 2012 Performing [Member] Real Estate Loans [Member] Home Equity [Member]	Mar. 31, 2013 Performing [Member] Consumer [Member]	Dec. 31, 2012 Performing [Member] Consumer [Member]	Mar. 31, 2013 Nonperforming [Member]	Dec. 31, 2012 Nonperforming [Member]	Mar. 31, 2013 Nonperforming [Member] Real Estate Loans [Member] Mortgages [Member]	Dec. 31, 2012 Nonperforming [Member] Real Estate Loans [Member] Mortgages [Member]	Mar. 31, 2013 Nonperforming [Member] Real Estate Loans [Member] Home Equity [Member]	Dec. 31, 2012 Nonperforming [Member] Real Estate Loans [Member] Home Equity [Member]	Mar. 31, 2013 Nonperforming [Member] Consumer [Member]	Dec. 31, 2012 Nonperforming [Member] Consumer [Member]
Financing Receivable, Recorded Investment [Line Items]
Percentage of dollar volume of commercial loan portfolio to be reviewed, minimum (in hundredths)			55.00%	60.00%
Amount over which all relationships to be reviewed, minimum			$ 500,000
Amount which is 90 days past due to be reviewed for all aggregate loan relationships, minimum			100,000
Financing Receivable by credit exposure [Abstract]
Total	$ 188,555,000	$ 188,639,000			$ 108,597,000	$ 106,548,000	$ 69,864,000	$ 71,532,000	$ 176,687,000	$ 176,710,000	$ 18,396,000	$ 18,015,000	$ 11,697,000	$ 12,011,000	$ 10,094,000	$ 10,559,000	$ 42,491,000	$ 41,620,000	$ 6,701,000	$ 6,260,000	$ 59,196,000	$ 59,208,000	$ 279,159,000	$ 277,785,000	$ 150,863,000	$ 149,892,000	$ 14,107,000	$ 13,690,000	$ 11,697,000	$ 12,011,000	$ 39,223,000	$ 39,239,000	$ 5,141,000	$ 4,833,000	$ 58,128,000	$ 58,120,000	$ 10,785,000	$ 11,417,000	$ 6,964,000	$ 7,616,000	$ 2,374,000	$ 2,386,000	$ 0	$ 0	$ 707,000	$ 826,000	$ 740,000	$ 589,000	$ 0	$ 0	$ 25,010,000	$ 24,547,000	$ 18,646,000	$ 19,127,000	$ 1,915,000	$ 1,939,000	$ 0	$ 0	$ 2,561,000	$ 1,555,000	$ 820,000	$ 838,000	$ 1,068,000	$ 1,088,000	$ 214,000	$ 75,000	$ 214,000	$ 75,000	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 315,168,000	$ 313,824,000	$ 187,732,000	$ 187,640,000	$ 108,005,000	$ 105,822,000	$ 69,670,000	$ 71,263,000	$ 10,057,000	$ 10,555,000	$ 823,000	$ 999,000	$ 592,000	$ 726,000	$ 194,000	$ 269,000	$ 37,000	$ 4,000