Loans (Schedule of Allowance for Loan Losses) (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	$ 14,808	$ 14,438	$ 14,929
Provision for Loan Losses	1,750	1,200	0
Recoveries	414	270	473
Loans Charged-off	(1,278)	(1,100)	(964)
Ending Balance	15,694	14,808	14,438
Commercial and Industrial Loans and Leases
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	3,725	4,242	4,627
Provision for Loan Losses	1,147	(483)	(451)
Recoveries	14	32	102
Loans Charged-off	(151)	(66)	(36)
Ending Balance	4,735	3,725	4,242
Commercial Real Estate Loans
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	5,452	6,342	7,273
Provision for Loan Losses	(689)	(846)	(688)
Recoveries	48	10	107
Loans Charged-off	(220)	(54)	(350)
Ending Balance	4,591	5,452	6,342
Agricultural Loans
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	4,094	2,115	1,123
Provision for Loan Losses	840	2,000	992
Recoveries	9	1	0
Loans Charged-off	(49)	(22)	0
Ending Balance	4,894	4,094	2,115
Home Equity Loans
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	283	383	246
Provision for Loan Losses	78	33	160
Recoveries	8	3	10
Loans Charged-off	(39)	(136)	(33)
Ending Balance	330	283	383
Consumer Loans
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	235	230	354
Provision for Loan Losses	517	273	(48)
Recoveries	272	208	236
Loans Charged-off	(726)	(476)	(312)
Ending Balance	298	235	230
Residential Mortgage Loans
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	329	414	622
Provision for Loan Losses	44	245	7
Recoveries	63	16	18
Loans Charged-off	(93)	(346)	(233)
Ending Balance	343	329	414
Unallocated
Allowance for Loan and Lease Losses [Roll Forward]
Beginning Balance	690	712	684
Provision for Loan Losses	(187)	(22)	28
Recoveries	0	0	0
Loans Charged-off	0	0	0
Ending Balance	$ 503	$ 690	$ 712

Amount of recovery of loans and lease receivables which had previously been fully or partially written-off as bad debts.

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Amount, after recoveries, of loans and leases that have been written-off.

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Amount of allowance to cover probable credit losses on loans and leases. Includes carryover of or adjustments to the allowance for loan losses in connection with business combinations. Excludes allowance for loans and leases covered under loss sharing agreements.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
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-Publisher FASB
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Amount of expense related to estimated loss from loan and lease transactions.

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-Name Accounting Standards Codification
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