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Loans and ALLL (Credit quality indicators for commercial and agricultural credit exposures) (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Financing Receivable, Credit Quality Indicator [Line Items]
Total	$ 1,248,558	$ 1,238,311
Total commercial [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total	757,993	756,686
Commercial real estate [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total	537,016	506,297
Commercial other [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total	174,000	200,131
Commercial Advances to Mortgage Brokers Segment [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total	46,977	50,258
Total agricultural [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total	93,782	100,461
Agricultural real estate [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total	66,109	71,218
Agricultural other [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total	27,673	29,243
Commercial And Agricultural Portfolio Segment [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total	851,775	857,147
1 - Excellent [Member] | Total commercial [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total	161	0
1 - Excellent [Member] | Commercial real estate [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total	0	0
1 - Excellent [Member] | Commercial other [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total	161	0
1 - Excellent [Member] | Commercial Advances to Mortgage Brokers Segment [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total	0	0
1 - Excellent [Member] | Total agricultural [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total	0	0
1 - Excellent [Member] | Agricultural real estate [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total	0	0
1 - Excellent [Member] | Agricultural other [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total	0	0
1 - Excellent [Member] | Commercial And Agricultural Portfolio Segment [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total	161	0
2 - High quality [Member] | Total commercial [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total	17,590	15,714
2 - High quality [Member] | Commercial real estate [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total	8,089	2,308
2 - High quality [Member] | Commercial other [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total	9,501	13,406
2 - High quality [Member] | Commercial Advances to Mortgage Brokers Segment [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total	0	0
2 - High quality [Member] | Total agricultural [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total	470	552
2 - High quality [Member] | Agricultural real estate [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total	462	541
2 - High quality [Member] | Agricultural other [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total	8	11
2 - High quality [Member] | Commercial And Agricultural Portfolio Segment [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total	18,060	16,266
3 - High satisfactory [Member] | Total commercial [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total	169,994	170,678
3 - High satisfactory [Member] | Commercial real estate [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total	79,462	69,327
3 - High satisfactory [Member] | Commercial other [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total	43,555	51,093
3 - High satisfactory [Member] | Commercial Advances to Mortgage Brokers Segment [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total	46,977	50,258
3 - High satisfactory [Member] | Total agricultural [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total	13,738	19,723
3 - High satisfactory [Member] | Agricultural real estate [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total	10,553	14,411
3 - High satisfactory [Member] | Agricultural other [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total	3,185	5,312
3 - High satisfactory [Member] | Commercial And Agricultural Portfolio Segment [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total	183,732	190,401
4 - Low satisfactory [Member] | Total commercial [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total	533,103	525,758
4 - Low satisfactory [Member] | Commercial real estate [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total	421,240	403,733
4 - Low satisfactory [Member] | Commercial other [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total	111,863	122,025
4 - Low satisfactory [Member] | Commercial Advances to Mortgage Brokers Segment [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total	0	0
4 - Low satisfactory [Member] | Total agricultural [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total	50,816	52,064
4 - Low satisfactory [Member] | Agricultural real estate [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total	34,263	34,464
4 - Low satisfactory [Member] | Agricultural other [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total	16,553	17,600
4 - Low satisfactory [Member] | Commercial And Agricultural Portfolio Segment [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total	583,919	577,822
5 - Special mention [Member] | Total commercial [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total	15,024	21,223
5 - Special mention [Member] | Commercial real estate [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total	12,880	15,049
5 - Special mention [Member] | Commercial other [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total	2,144	6,174
5 - Special mention [Member] | Commercial Advances to Mortgage Brokers Segment [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total	0	0
5 - Special mention [Member] | Total agricultural [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total	17,618	16,377
5 - Special mention [Member] | Agricultural real estate [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total	13,827	13,137
5 - Special mention [Member] | Agricultural other [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total	3,791	3,240
5 - Special mention [Member] | Commercial And Agricultural Portfolio Segment [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total	32,642	37,600
6 - Substandard [Member] | Total commercial [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total	21,960	21,984
6 - Substandard [Member] | Commercial real estate [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total	15,308	15,854
6 - Substandard [Member] | Commercial other [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total	6,652	6,130
6 - Substandard [Member] | Commercial Advances to Mortgage Brokers Segment [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total	0	0
6 - Substandard [Member] | Total agricultural [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total	8,329	7,960
6 - Substandard [Member] | Agricultural real estate [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total	4,468	5,267
6 - Substandard [Member] | Agricultural other [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total	3,861	2,693
6 - Substandard [Member] | Commercial And Agricultural Portfolio Segment [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total	30,289	29,944
7 - Vulnerable [Member] | Total commercial [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total	161	1,329
7 - Vulnerable [Member] | Commercial real estate [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total	37	26
7 - Vulnerable [Member] | Commercial other [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total	124	1,303
7 - Vulnerable [Member] | Commercial Advances to Mortgage Brokers Segment [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total	0	0
7 - Vulnerable [Member] | Total agricultural [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total	2,811	3,595
7 - Vulnerable [Member] | Agricultural real estate [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total	2,536	3,208
7 - Vulnerable [Member] | Agricultural other [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total	275	387
7 - Vulnerable [Member] | Commercial And Agricultural Portfolio Segment [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total	2,972	4,924
8 - Doubtful [Member] | Total commercial [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total	0	0
8 - Doubtful [Member] | Commercial real estate [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total	0	0
8 - Doubtful [Member] | Commercial other [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total	0	0
8 - Doubtful [Member] | Commercial Advances to Mortgage Brokers Segment [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total	0	0
8 - Doubtful [Member] | Total agricultural [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total	0	190
8 - Doubtful [Member] | Agricultural real estate [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total	0	190
8 - Doubtful [Member] | Agricultural other [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total	0	0
8 - Doubtful [Member] | Commercial And Agricultural Portfolio Segment [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total	0	190
Loss [Member] | Total commercial [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total	0	0
Loss [Member] | Commercial real estate [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total	0	0
Loss [Member] | Commercial other [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total	0	0
Loss [Member] | Commercial Advances to Mortgage Brokers Segment [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total	0	0
Loss [Member] | Total agricultural [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total	0	0
Loss [Member] | Agricultural real estate [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total	0	0
Loss [Member] | Agricultural other [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total	0	0
Loss [Member] | Commercial And Agricultural Portfolio Segment [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total	$ 0	$ 0

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