Allowance for Credit Losses, Loans by Class Modified as Troubled Debt Restructured Loans (Details) (USD $)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2013 Loan	Jun. 30, 2012 Loan	Jun. 30, 2013 Loan	Jun. 30, 2012 Loan	Dec. 31, 2012 Loan
Financing Receivable, Modifications [Line Items]
Specific reserves	$ 433,000	$ 190,000	$ 433,000	$ 190,000	$ 401,000
Troubled debt restructured loans	2,100,000	1,700,000	2,100,000	1,700,000	2,600,000
Commitments to lend additional amounts to customers with outstanding loans that are classified as troubled debt restructurings	0	0	0	0	0
Period of modifications involving a reduction of stated interest rate of the loan			5 years	5 years
Loans by class modified as troubled debt restructured loans [Abstract]
Number of Loans	1	4	8	12	18
Pre-Modification Outstanding Recorded Investment	180,000	471,000	793,000	1,083,000	2,033,000
Post-Modification Outstanding Recorded Investment	169,000	434,000	766,000	1,034,000	1,969,000
Increase in allowance for credit losses due to TDR	0	85,000	4,000	29,000	53,000
TDR's charge-offs	11,000	37,000	27,000	49,000	64,000
Charge offs on troubled debt restructurings that subsequently defaulted	0	0	0	0	0
Period after which loan is considered to be in payment default			90 days
Minimum [Member]
Financing Receivable, Modifications [Line Items]
Period of modifications involving a reduction of stated interest rate of the loan					2 years
Period of modifications involving extension of maturity date			6 months	6 months	6 months
Maximum [Member]
Financing Receivable, Modifications [Line Items]
Period of modifications involving a reduction of stated interest rate of the loan					5 years
Period of modifications involving extension of maturity date			10 years	15 years	10 years
Performing [Member]
Financing Receivable, Modifications [Line Items]
Troubled debt restructured loans, performing	1,600,000	1,400,000	1,600,000	1,400,000	2,300,000
Commercial Real Estate [Member]
Loans by class modified as troubled debt restructured loans [Abstract]
Number of Loans		0		1	1
Pre-Modification Outstanding Recorded Investment		0		116,000	116,000
Post-Modification Outstanding Recorded Investment		0		116,000	116,000
Residential 1st Mortgages [Member]
Loans by class modified as troubled debt restructured loans [Abstract]
Number of Loans	0	1	4	4	2
Pre-Modification Outstanding Recorded Investment	0	30,000	306,000	146,000	216,000
Post-Modification Outstanding Recorded Investment	0	29,000	290,000	139,000	201,000
Home Equity Lines & Loans [Member]
Loans by class modified as troubled debt restructured loans [Abstract]
Number of Loans	1	2	2	3	7
Pre-Modification Outstanding Recorded Investment	180,000	294,000	195,000	368,000	529,000
Post-Modification Outstanding Recorded Investment	169,000	258,000	184,000	326,000	480,000
Agricultural [Member]
Loans by class modified as troubled debt restructured loans [Abstract]
Number of Loans		0		1	4
Pre-Modification Outstanding Recorded Investment		0		180,000	858,000
Post-Modification Outstanding Recorded Investment		0		180,000	858,000
Commercial [Member]
Loans by class modified as troubled debt restructured loans [Abstract]
Number of Loans	0	1	2	3	3
Pre-Modification Outstanding Recorded Investment	0	147,000	292,000	273,000	273,000
Post-Modification Outstanding Recorded Investment	0	147,000	292,000	273,000	273,000
Consumer & Other [Member]
Loans by class modified as troubled debt restructured loans [Abstract]
Number of Loans					1
Pre-Modification Outstanding Recorded Investment					41,000
Post-Modification Outstanding Recorded Investment					$ 41,000