Loans and ALLL (Summary of changes in ALLL by segments) (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans and Leases Receivable, Allowance	$ 7,700	$ 7,400
Summary of changes in the ALLL and the recorded investment in loans by segments
Allowance for loan losses, Beginning Balance	7,400	7,400
Allowance for loan losses, Charge-offs	(771)	(916)
Allowance for loan losses, Recoveries	818	1,051
Allowance for loan losses, Provision for loan losses	253	(135)	$ (2,771)
Allowance for loan losses, Ending Balance	7,700	7,400	7,400
Commercial [Member]
Summary of changes in the ALLL and the recorded investment in loans by segments
Allowance for loan losses, Beginning Balance	1,814	2,171
Allowance for loan losses, Charge-offs	(265)	(57)
Allowance for loan losses, Recoveries	453	448
Allowance for loan losses, Provision for loan losses	(296)	(748)
Allowance for loan losses, Ending Balance	1,706	1,814	2,171
Agricultural [Member]
Summary of changes in the ALLL and the recorded investment in loans by segments
Allowance for loan losses, Beginning Balance	884	329
Allowance for loan losses, Charge-offs	0	0
Allowance for loan losses, Recoveries	0	92
Allowance for loan losses, Provision for loan losses	(273)	463
Allowance for loan losses, Ending Balance	611	884	329
Residential Real Estate [Member]
Summary of changes in the ALLL and the recorded investment in loans by segments
Allowance for loan losses, Beginning Balance	2,664	3,330
Allowance for loan losses, Charge-offs	(200)	(574)
Allowance for loan losses, Recoveries	206	287
Allowance for loan losses, Provision for loan losses	(107)	(379)
Allowance for loan losses, Ending Balance	2,563	2,664	3,330
Consumer [Member]
Summary of changes in the ALLL and the recorded investment in loans by segments
Allowance for loan losses, Beginning Balance	624	522
Allowance for loan losses, Charge-offs	(306)	(285)
Allowance for loan losses, Recoveries	159	224
Allowance for loan losses, Provision for loan losses	423	163
Allowance for loan losses, Ending Balance	900	624	522
Unallocated [Member]
Summary of changes in the ALLL and the recorded investment in loans by segments
Allowance for loan losses, Beginning Balance	1,414	1,048
Allowance for loan losses, Charge-offs	0	0
Allowance for loan losses, Recoveries	0	0
Allowance for loan losses, Provision for loan losses	506	366
Allowance for loan losses, Ending Balance	$ 1,920	$ 1,414	$ 1,048

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

No definition available.

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- Definition

A valuation allowance for financing receivables that are expected to be uncollectible.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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No definition available.

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Amount of recovery of financing receivables doubtful of collection that were previously charged off.

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Amount of direct write-downs of financing receivables charged against the allowance.

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- Definition

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
-Paragraph 11B
-Subparagraph (g)
-URI http://asc.fasb.org/extlink&oid=66008989&loc=SL6953423-111524

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=66008989&loc=SL6953423-111524

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.7(d))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
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-Section S99
-Paragraph 4
-Subparagraph (SAB Topic 6.L.1)
-URI http://asc.fasb.org/extlink&oid=27010918&loc=d3e74567-122707

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 30
-Section 50
-Paragraph 2
-Subparagraph (b)(1)(ii)
-URI http://asc.fasb.org/extlink&oid=6379141&loc=d3e15032-111544

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Amount of expense related loan transactions, lease transactions, credit loss from transactions other than loan and lease transactions, and other loss based on assessment of uncollectability from the counterparty to reduce the account to their net realizable value.

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