Allowance for Loan Losses and Credit Quality of Loans, Impaired Loans (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Allowance for Loan Losses and Credit Quality of Loans [Abstract]
Threshold balance for classified loans to be evaluated individually for impairment	$ 750
Total [Abstract]
Recorded investment balance (book)	21,082	$ 21,138
Unpaid principal balance (legal)	28,690	28,120
Related allowance	42	57
Acquired impaired loans specifically evaluated for impairment	0	0
Originated Loans [Member]
With an allowance recorded [Abstract]
Recorded investment balance (book)	20,981	21,035
Unpaid principal balance (legal)	28,583	28,011
Originated Loans [Member] \| Commercial Loans [Member]
With no related allowance recorded [Abstract]
Recorded investment balance (book)	5,905	5,773
Unpaid principal balance (legal)	9,193	8,848
With an allowance recorded [Abstract]
Recorded investment balance (book)	101	103
Unpaid principal balance (legal)	107	109
Total [Abstract]
Related allowance	42	57
Originated Loans [Member] \| Commercial Loans [Member] \| C&I [Member]
With no related allowance recorded [Abstract]
Recorded investment balance (book)	430
Unpaid principal balance (legal)	696
With an allowance recorded [Abstract]
Recorded investment balance (book)	27
Unpaid principal balance (legal)	26
Total [Abstract]
Related allowance	27
Originated Loans [Member] \| Commercial Loans [Member] \| CRE [Member]
With no related allowance recorded [Abstract]
Recorded investment balance (book)	4,397
Unpaid principal balance (legal)	6,362
With an allowance recorded [Abstract]
Recorded investment balance (book)	74
Unpaid principal balance (legal)	81
Total [Abstract]
Related allowance	15
Originated Loans [Member] \| Commercial Loans [Member] \| Commercial [Member]
With no related allowance recorded [Abstract]
Recorded investment balance (book)		0
Unpaid principal balance (legal)		251
Originated Loans [Member] \| Commercial Loans [Member] \| Commercial Real Estate [Member]
With no related allowance recorded [Abstract]
Recorded investment balance (book)		2,211
Unpaid principal balance (legal)		3,979
With an allowance recorded [Abstract]
Recorded investment balance (book)		76
Unpaid principal balance (legal)		82
Total [Abstract]
Related allowance		30
Originated Loans [Member] \| Commercial Loans [Member] \| Agricultural [Member]
With no related allowance recorded [Abstract]
Recorded investment balance (book)		452
Unpaid principal balance (legal)		465
With an allowance recorded [Abstract]
Recorded investment balance (book)		27
Unpaid principal balance (legal)		27
Total [Abstract]
Related allowance		27
Originated Loans [Member] \| Commercial Loans [Member] \| Agricultural Real Estate [Member]
With no related allowance recorded [Abstract]
Recorded investment balance (book)		2,250
Unpaid principal balance (legal)		2,423
Originated Loans [Member] \| Commercial Loans [Member] \| Business Banking [Member]
With no related allowance recorded [Abstract]
Recorded investment balance (book)	1,078	860
Unpaid principal balance (legal)	2,135	1,730
Originated Loans [Member] \| Consumer Loans [Member]
With no related allowance recorded [Abstract]
Recorded investment balance (book)	8,305	8,432
Unpaid principal balance (legal)	10,293	10,383
Originated Loans [Member] \| Consumer Loans [Member] \| Dealer Finance [Member]
With no related allowance recorded [Abstract]
Recorded investment balance (book)	198
Unpaid principal balance (legal)	216
Originated Loans [Member] \| Consumer Loans [Member] \| Direct [Member]
With no related allowance recorded [Abstract]
Recorded investment balance (book)	8,107
Unpaid principal balance (legal)	10,077
Originated Loans [Member] \| Consumer Loans [Member] \| Indirect [Member]
With no related allowance recorded [Abstract]
Recorded investment balance (book)		131
Unpaid principal balance (legal)		143
Originated Loans [Member] \| Consumer Loans [Member] \| Home Equity [Member]
With no related allowance recorded [Abstract]
Recorded investment balance (book)		8,027
Unpaid principal balance (legal)		9,966
Originated Loans [Member] \| Consumer Loans [Member] \| Direct [Member]
With no related allowance recorded [Abstract]
Recorded investment balance (book)		274
Unpaid principal balance (legal)		274
Originated Loans [Member] \| Residential Real Estate Mortgages [Member]
With an allowance recorded [Abstract]
Recorded investment balance (book)	6,771	6,830
Unpaid principal balance (legal)	$ 9,097	$ 8,780

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Amount of financing receivables related to acquired loans that were individually evaluated for impairment.

+ References

No definition available.

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The threshold balance for classified loans to be individually evaluated for impairment.

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Amount of investment of impaired financing receivables with related allowance for credit losses and without a related allowance for credit losses.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 14A
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953550-111524

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Amount of allowance for credit losses related to recorded investment.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 15
-Subparagraph (a)(3)
-URI http://asc.fasb.org/extlink&oid=84173941&loc=d3e5212-111524

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Amount of unpaid principal balance of impaired financing receivables with related allowance for credit losses and without related allowance for credit losses.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 15
-Subparagraph (a)(4)
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Amount of investment in impaired financing receivables for which there is no related allowance for credit losses.

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Amount of unpaid principal balance of impaired financing receivables for which there is no related allowance for credit losses.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 15
-Subparagraph (a)(4)
-URI http://asc.fasb.org/extlink&oid=84173941&loc=d3e5212-111524

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Amount of investment in impaired financing receivables for which there is a related allowance for credit losses.

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+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 15
-Subparagraph (a)(4)
-URI http://asc.fasb.org/extlink&oid=84173941&loc=d3e5212-111524

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