Allowance for Loan Losses and Credit Quality of Loans, Impaired Loans (Details) (USD $)	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012
Allowance for Loan Losses and Credit Quality of Loans [Abstract]
Minimum balance for classified loans to be evaluated individually for impairment	$ 500,000
Financing Receivable, Impaired [Line Items]
Recorded Investment Balance (Book)	33,658,000		33,028,000
Unpaid Principal Balance (Legal)	42,571,000		39,148,000
Related Allowance	607,000		2,848,000
Average Recorded Investment	34,316,000	24,991,000
Interest Income Recognized Accrual	222,000	242,000
Interest Income Recognized Cash	222,000	242,000
With No Allowance Recorded [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment Balance (Book)	29,590,000		24,625,000
Unpaid Principal Balance (Legal)	36,882,000		28,967,000
Average Recorded Investment	30,248,000	23,559,000
Interest Income Recognized Accrual	222,000	195,000
Interest Income Recognized Cash	222,000	195,000
With No Allowance Recorded [Member] | Commercial Loans [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment Balance (Book)	24,658,000		20,061,000
Unpaid Principal Balance (Legal)	31,391,000		24,154,000
With No Allowance Recorded [Member] | Commercial Loans [Member] | Commercial [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment Balance (Book)	5,106,000		1,651,000
Unpaid Principal Balance (Legal)	7,374,000		1,710,000
Average Recorded Investment	6,038,000	1,974,000
Interest Income Recognized Accrual	15,000	14,000
Interest Income Recognized Cash	15,000	14,000
With No Allowance Recorded [Member] | Commercial Loans [Member] | Commercial Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment Balance (Book)	8,461,000		8,709,000
Unpaid Principal Balance (Legal)	9,156,000		9,553,000
Average Recorded Investment	8,545,000	5,821,000
Interest Income Recognized Accrual	61,000	15,000
Interest Income Recognized Cash	61,000	15,000
With No Allowance Recorded [Member] | Commercial Loans [Member] | Agricultural [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment Balance (Book)	873,000		940,000
Unpaid Principal Balance (Legal)	1,269,000		1,286,000
Average Recorded Investment	1,004,000	3,117,000
Interest Income Recognized Accrual	11,000	45,000
Interest Income Recognized Cash	11,000	45,000
With No Allowance Recorded [Member] | Commercial Loans [Member] | Agricultural Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment Balance (Book)	1,833,000		1,713,000
Unpaid Principal Balance (Legal)	2,163,000		2,026,000
Average Recorded Investment	1,841,000	1,977,000
Interest Income Recognized Accrual	17,000	17,000
Interest Income Recognized Cash	17,000	17,000
With No Allowance Recorded [Member] | Commercial Loans [Member] | Business Banking [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment Balance (Book)	8,385,000		7,048,000
Unpaid Principal Balance (Legal)	11,429,000		9,579,000
Average Recorded Investment	8,189,000	7,730,000
Interest Income Recognized Accrual	54,000	60,000
Interest Income Recognized Cash	54,000	60,000
With No Allowance Recorded [Member] | Consumer Loans [Member] | Home Equity [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment Balance (Book)	2,910,000		2,553,000
Unpaid Principal Balance (Legal)	3,084,000		2,657,000
Average Recorded Investment	2,643,000	1,909,000
Interest Income Recognized Accrual	39,000	31,000
Interest Income Recognized Cash	39,000	31,000
With No Allowance Recorded [Member] | Residential Real Estate Mortgages [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment Balance (Book)	2,022,000		2,011,000
Unpaid Principal Balance (Legal)	2,407,000		2,308,000
Average Recorded Investment	1,988,000	1,031,000
Interest Income Recognized Accrual	25,000	13,000
Interest Income Recognized Cash	25,000	13,000
With An Allowance Recorded [Member] | Commercial Loans [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment Balance (Book)	4,068,000		8,403,000
Unpaid Principal Balance (Legal)	5,689,000		10,029,000
Related Allowance	607,000		2,848,000
Average Recorded Investment	4,068,000	1,432,000
Interest Income Recognized Accrual	0	47,000
Interest Income Recognized Cash	0	47,000
With An Allowance Recorded [Member] | Commercial Loans [Member] | Commercial [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment Balance (Book)	0		4,335,000
Unpaid Principal Balance (Legal)	0		4,340,000
Related Allowance	0		2,241,000
Average Recorded Investment	0	1,432,000
Interest Income Recognized Accrual	0	47,000
Interest Income Recognized Cash	0	47,000
With An Allowance Recorded [Member] | Commercial Loans [Member] | Commercial Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment Balance (Book)	4,068,000		4,068,000
Unpaid Principal Balance (Legal)	5,689,000		5,689,000
Related Allowance	607,000		607,000
Average Recorded Investment	4,068,000	0
Interest Income Recognized Accrual	0	0
Interest Income Recognized Cash	$ 0	$ 0