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Loans and ALLL (Credit quality indicators for commercial and agricultural credit exposures) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Financing Receivable, Recorded Investment [Line Items]
Total	$ 1,186,570	$ 1,128,707
Total commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	700,941	659,529
Commercial real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	510,153	497,687
Commercial other [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	155,265	150,049
Commercial Advances to Mortgage Brokers Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	35,523	11,793
Total agricultural [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	116,920	127,161
Agricultural real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	80,027	87,320
Agricultural other [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	36,893	39,841
Commercial And Agricultural Portfolio Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	817,861	786,690
1 - Excellent [Member] | Total commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	390	52
1 - Excellent [Member] | Commercial real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	0	21
1 - Excellent [Member] | Commercial other [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	390	31
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	0	79
1 - Excellent [Member] | Agricultural real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	0	51
1 - Excellent [Member] | Agricultural other [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	0	28
1 - Excellent [Member] | Commercial And Agricultural Portfolio Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	390	131
2 - High quality [Member] | Total commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	11,426	18,037
2 - High quality [Member] | Commercial real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	2,582	4,564
2 - High quality [Member] | Commercial other [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	8,844	13,473
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	1,551	3,342
2 - High quality [Member] | Agricultural real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	1,452	2,729
2 - High quality [Member] | Agricultural other [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	99	613
2 - High quality [Member] | Commercial And Agricultural Portfolio Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	12,977	21,379
3 - High satisfactory [Member] | Total commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	188,118	182,565
3 - High satisfactory [Member] | Commercial real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	109,737	127,573
3 - High satisfactory [Member] | Commercial other [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	42,858	43,199
3 - High satisfactory [Member] | Commercial Advances to Mortgage Brokers Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	35,523	11,793
3 - High satisfactory [Member] | Total agricultural [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	23,534	25,364
3 - High satisfactory [Member] | Agricultural real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	16,765	18,325
3 - High satisfactory [Member] | Agricultural other [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	6,769	7,039
3 - High satisfactory [Member] | Commercial And Agricultural Portfolio Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	211,652	207,929
4 - Low satisfactory [Member] | Total commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	472,045	429,554
4 - Low satisfactory [Member] | Commercial real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	377,198	344,920
4 - Low satisfactory [Member] | Commercial other [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	94,847	84,634
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	63,659	65,980
4 - Low satisfactory [Member] | Agricultural real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	42,798	46,636
4 - Low satisfactory [Member] | Agricultural other [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	20,861	19,344
4 - Low satisfactory [Member] | Commercial And Agricultural Portfolio Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	535,704	495,534
5 - Special mention [Member] | Total commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	18,842	18,134
5 - Special mention [Member] | Commercial real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	15,372	12,847
5 - Special mention [Member] | Commercial other [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	3,470	5,287
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	10,919	16,144
5 - Special mention [Member] | Agricultural real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	7,165	10,520
5 - Special mention [Member] | Agricultural other [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	3,754	5,624
5 - Special mention [Member] | Commercial And Agricultural Portfolio Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	29,761	34,278
6 - Substandard [Member] | Total commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	8,499	9,430
6 - Substandard [Member] | Commercial real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	4,874	7,428
6 - Substandard [Member] | Commercial other [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	3,625	2,002
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	12,972	11,303
6 - Substandard [Member] | Agricultural real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	9,136	6,343
6 - Substandard [Member] | Agricultural other [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	3,836	4,960
6 - Substandard [Member] | Commercial And Agricultural Portfolio Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	21,471	20,733
7 - Vulnerable [Member] | Total commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	1,621	1,757
7 - Vulnerable [Member] | Commercial real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	390	334
7 - Vulnerable [Member] | Commercial other [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	1,231	1,423
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	4,285	4,949
7 - Vulnerable [Member] | Agricultural real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	2,711	2,716
7 - Vulnerable [Member] | Agricultural other [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	1,574	2,233
7 - Vulnerable [Member] | Commercial And Agricultural Portfolio Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	5,906	6,706
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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