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Loans and ALLL (Credit quality indicators for commercial and agricultural credit exposures) (Details) - USD ($) $ in Thousands | Sep. 30, 2018 | Dec. 31, 2017
--- | --- | ---
Financing Receivable, Recorded Investment [Line Items] |  |
Total | $ 1,139,930 | $ 1,091,519
Total commercial [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Total | 668,915 | 634,759
Commercial real estate [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Total | 504,886 | 481,654
Commercial other [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Total | 148,398 | 141,024
Commercial Advances to Mortgage Brokers Segment [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Total | 15,631 | 12,081
Total agricultural [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Total | 129,232 | 128,269
Agricultural real estate [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Total | 87,734 | 88,165
Agricultural other [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Total | 41,498 | 40,104
Commercial And Agricultural Portfolio Segment [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Total | 798,147 | 763,028
1 - Excellent [Member] | Total commercial [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Total | 64 | 340
1 - Excellent [Member] | Commercial real estate [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Total | 22 | 24
1 - Excellent [Member] | Commercial other [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Total | 42 | 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 | 86 | 34
1 - Excellent [Member] | Agricultural real estate [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Total | 52 | 0
1 - Excellent [Member] | Agricultural other [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Total | 34 | 34
1 - Excellent [Member] | Commercial And Agricultural Portfolio Segment [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Total | 150 | 374
2 - High quality [Member] | Total commercial [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Total | 21,773 | 20,664
2 - High quality [Member] | Commercial real estate [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Total | 4,518 | 8,402
2 - High quality [Member] | Commercial other [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Total | 17,255 | 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 | 3,577 | 3,933
2 - High quality [Member] | Agricultural real estate [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Total | 2,947 | 2,909
2 - High quality [Member] | Agricultural other [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Total | 630 | 1,024
2 - High quality [Member] | Commercial And Agricultural Portfolio Segment [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Total | 25,350 | 24,597
3 - High satisfactory [Member] | Total commercial [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Total | 180,508 | 190,575
3 - High satisfactory [Member] | Commercial real estate [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Total | 125,083 | 131,826
3 - High satisfactory [Member] | Commercial other [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Total | 39,794 | 46,668
3 - High satisfactory [Member] | Commercial Advances to Mortgage Brokers Segment [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Total | 15,631 | 12,081
3 - High satisfactory [Member] | Total agricultural [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Total | 26,768 | 29,939
3 - High satisfactory [Member] | Agricultural real estate [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Total | 19,137 | 21,072
3 - High satisfactory [Member] | Agricultural other [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Total | 7,631 | 8,867
3 - High satisfactory [Member] | Commercial And Agricultural Portfolio Segment [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Total | 207,276 | 220,514
4 - Low satisfactory [Member] | Total commercial [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Total | 443,461 | 401,757
4 - Low satisfactory [Member] | Commercial real estate [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Total | 356,325 | 326,166
4 - Low satisfactory [Member] | Commercial other [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Total | 87,136 | 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 | 65,341 | 66,302
4 - Low satisfactory [Member] | Agricultural real estate [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Total | 45,854 | 47,835
4 - Low satisfactory [Member] | Agricultural other [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Total | 19,487 | 18,467
4 - Low satisfactory [Member] | Commercial And Agricultural Portfolio Segment [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Total | 508,802 | 468,059
5 - Special mention [Member] | Total commercial [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Total | 13,534 | 12,875
5 - Special mention [Member] | Commercial real estate [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Total | 11,739 | 8,986
5 - Special mention [Member] | Commercial other [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Total | 1,795 | 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 | 16,228 | 19,039
5 - Special mention [Member] | Agricultural real estate [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Total | 10,445 | 10,493
5 - Special mention [Member] | Agricultural other [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Total | 5,783 | 8,546
5 - Special mention [Member] | Commercial And Agricultural Portfolio Segment [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Total | 29,762 | 31,914
6 - Substandard [Member] | Total commercial [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Total | 8,435 | 7,819
6 - Substandard [Member] | Commercial real estate [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Total | 6,302 | 5,521
6 - Substandard [Member] | Commercial other [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Total | 2,133 | 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 | 11,934 | 7,072
6 - Substandard [Member] | Agricultural real estate [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Total | 6,418 | 4,325
6 - Substandard [Member] | Agricultural other [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Total | 5,516 | 2,747
6 - Substandard [Member] | Commercial And Agricultural Portfolio Segment [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Total | 20,369 | 14,891
7 - Vulnerable [Member] | Total commercial [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Total | 1,140 | 729
7 - Vulnerable [Member] | Commercial real estate [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Total | 897 | 729
7 - Vulnerable [Member] | Commercial other [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Total | 243 | 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 | 5,298 | 1,950
7 - Vulnerable [Member] | Agricultural real estate [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Total | 2,881 | 1,531
7 - Vulnerable [Member] | Agricultural other [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Total | 2,417 | 419
7 - Vulnerable [Member] | Commercial And Agricultural Portfolio Segment [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Total | 6,438 | 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
9 - Unlikely to be Collected Financing Receivable [Member] | Commercial real estate [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Total | $ 0 | $ 0

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