Credit Quality and Related Allowance for Loan Losses (Details 4) (USD $)	3 Months Ended
	Mar. 31, 2013 category	Dec. 31, 2012
Credit Quality and Related Allowance for Loan Losses
Minimum period after which loans are considered as substandard	90 days
Minimum amount after which external annual loan review is performed	$ 800,000
Credit quality categories
Total	513,449,000	513,354,000
Number of categories considered not criticized and rated as "Pass"	6
Commercial and Agricultural
Credit quality categories
Total	46,555,000	48,455,000
Residential Real Estate Mortgages
Credit quality categories
Total	261,784,000	252,142,000
Commercial Real Estate Mortgage
Credit quality categories
Total	178,661,000	182,031,000
Construction Real Estate Mortgage
Credit quality categories
Total	15,558,000	20,067,000
Installment Loans to Individuals
Credit quality categories
Total	10,891,000	10,659,000
Pass
Credit quality categories
Total	491,929,000	489,032,000
Pass | Commercial and Agricultural
Credit quality categories
Total	44,991,000	46,805,000
Pass | Residential Real Estate Mortgages
Credit quality categories
Total	260,193,000	250,161,000
Pass | Commercial Real Estate Mortgage
Credit quality categories
Total	164,218,000	167,463,000
Pass | Construction Real Estate Mortgage
Credit quality categories
Total	11,638,000	13,944,000
Pass | Installment Loans to Individuals
Credit quality categories
Total	10,889,000	10,659,000
Special Mention
Credit quality categories
Total	3,014,000	3,110,000
Special Mention | Commercial and Agricultural
Credit quality categories
Total	1,420,000	1,480,000
Special Mention | Commercial Real Estate Mortgage
Credit quality categories
Total	1,594,000	1,630,000
Substandard
Credit quality categories
Total	18,506,000	21,212,000
Substandard | Commercial and Agricultural
Credit quality categories
Total	144,000	170,000
Substandard | Residential Real Estate Mortgages
Credit quality categories
Total	1,591,000	1,981,000
Substandard | Commercial Real Estate Mortgage
Credit quality categories
Total	12,849,000	12,938,000
Substandard | Construction Real Estate Mortgage
Credit quality categories
Total	3,920,000	6,123,000
Substandard | Installment Loans to Individuals
Credit quality categories
Total	$ 2,000