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Loans and ALLL (Credit quality indicators for commercial and agricultural credit exposures) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Financing Receivable, Recorded Investment [Line Items]
Total	$ 1,128,707	$ 1,091,519
Total commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	659,529	634,759
Commercial real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	497,687	481,654
Commercial other [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	150,049	141,024
Commercial Advances to Mortgage Brokers Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	11,793	12,081
Total agricultural [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	127,161	128,269
Agricultural real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	87,320	88,165
Agricultural other [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	39,841	40,104
Commercial And Agricultural Portfolio Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	786,690	763,028
1 - Excellent [Member] | Total commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	52	340
1 - Excellent [Member] | Commercial real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	21	24
1 - Excellent [Member] | Commercial other [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	31	316
1 - Excellent [Member] | Commercial Advances to Mortgage Brokers Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	0	0
1 - Excellent [Member] | Total agricultural [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	79	34
1 - Excellent [Member] | Agricultural real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	51	0
1 - Excellent [Member] | Agricultural other [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	28	34
1 - Excellent [Member] | Commercial And Agricultural Portfolio Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	131	374
2 - High quality [Member] | Total commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	18,037	20,664
2 - High quality [Member] | Commercial real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	4,564	8,402
2 - High quality [Member] | Commercial other [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	13,473	12,262
2 - High quality [Member] | Commercial Advances to Mortgage Brokers Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	0	0
2 - High quality [Member] | Total agricultural [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	3,342	3,933
2 - High quality [Member] | Agricultural real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	2,729	2,909
2 - High quality [Member] | Agricultural other [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	613	1,024
2 - High quality [Member] | Commercial And Agricultural Portfolio Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	21,379	24,597
3 - High satisfactory [Member] | Total commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	182,565	190,575
3 - High satisfactory [Member] | Commercial real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	127,573	131,826
3 - High satisfactory [Member] | Commercial other [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	43,199	46,668
3 - High satisfactory [Member] | Commercial Advances to Mortgage Brokers Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	11,793	12,081
3 - High satisfactory [Member] | Total agricultural [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	25,364	29,939
3 - High satisfactory [Member] | Agricultural real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	18,325	21,072
3 - High satisfactory [Member] | Agricultural other [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	7,039	8,867
3 - High satisfactory [Member] | Commercial And Agricultural Portfolio Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	207,929	220,514
4 - Low satisfactory [Member] | Total commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	429,554	401,757
4 - Low satisfactory [Member] | Commercial real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	344,920	326,166
4 - Low satisfactory [Member] | Commercial other [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	84,634	75,591
4 - Low satisfactory [Member] | Commercial Advances to Mortgage Brokers Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	0	0
4 - Low satisfactory [Member] | Total agricultural [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	65,980	66,302
4 - Low satisfactory [Member] | Agricultural real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	46,636	47,835
4 - Low satisfactory [Member] | Agricultural other [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	19,344	18,467
4 - Low satisfactory [Member] | Commercial And Agricultural Portfolio Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	495,534	468,059
5 - Special mention [Member] | Total commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	18,134	12,875
5 - Special mention [Member] | Commercial real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	12,847	8,986
5 - Special mention [Member] | Commercial other [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	5,287	3,889
5 - Special mention [Member] | Commercial Advances to Mortgage Brokers Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	0	0
5 - Special mention [Member] | Total agricultural [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	16,144	19,039
5 - Special mention [Member] | Agricultural real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	10,520	10,493
5 - Special mention [Member] | Agricultural other [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	5,624	8,546
5 - Special mention [Member] | Commercial And Agricultural Portfolio Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	34,278	31,914
6 - Substandard [Member] | Total commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	9,430	7,819
6 - Substandard [Member] | Commercial real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	7,428	5,521
6 - Substandard [Member] | Commercial other [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	2,002	2,298
6 - Substandard [Member] | Commercial Advances to Mortgage Brokers Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	0	0
6 - Substandard [Member] | Total agricultural [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	11,303	7,072
6 - Substandard [Member] | Agricultural real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	6,343	4,325
6 - Substandard [Member] | Agricultural other [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	4,960	2,747
6 - Substandard [Member] | Commercial And Agricultural Portfolio Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	20,733	14,891
7 - Vulnerable [Member] | Total commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	1,757	729
7 - Vulnerable [Member] | Commercial real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	334	729
7 - Vulnerable [Member] | Commercial other [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	1,423	0
7 - Vulnerable [Member] | Commercial Advances to Mortgage Brokers Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	0	0
7 - Vulnerable [Member] | Total agricultural [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	4,949	1,950
7 - Vulnerable [Member] | Agricultural real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	2,716	1,531
7 - Vulnerable [Member] | Agricultural other [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	2,233	419
7 - Vulnerable [Member] | Commercial And Agricultural Portfolio Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	6,706	2,679
8 - Doubtful [Member] | Total commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	0	0
8 - Doubtful [Member] | Commercial real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	0	0
8 - Doubtful [Member] | Commercial other [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	0	0
8 - Doubtful [Member] | Commercial Advances to Mortgage Brokers Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	0	0
8 - Doubtful [Member] | Total agricultural [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	0	0
8 - Doubtful [Member] | Agricultural real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	0	0
8 - Doubtful [Member] | Agricultural other [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	0	0
8 - Doubtful [Member] | Commercial And Agricultural Portfolio Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	0	0
Loss [Member] | Total commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	0	0
Loss [Member] | Commercial real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	0	0
Loss [Member] | Commercial other [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	0	0
Loss [Member] | Commercial Advances to Mortgage Brokers Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	0	0
Loss [Member] | Total agricultural [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	0	0
Loss [Member] | Agricultural real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	0	0
Loss [Member] | Agricultural other [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	0	0
Loss [Member] | Commercial And Agricultural Portfolio Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	$ 0	$ 0

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+ References

No definition available.

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+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.10(3))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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