Loans and ALLL (Credit quality indicators for commercial and agricultural credit exposures) (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Financing Receivable, Recorded Investment [Line Items]
Total	$ 919,594	$ 850,492
Total commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	500,374	448,381
Commercial real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	380,789	343,617
Commercial other [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	119,585	104,764
Total agricultural [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	126,517	115,911
Agricultural real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	82,582	76,542
Agricultural other [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	43,935	39,369
1 - Excellent [Member] | Total commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	982	499
1 - Excellent [Member] | Commercial real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	0	0
1 - Excellent [Member] | Commercial other [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	982	499
1 - Excellent [Member] | Total agricultural [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	0	0
1 - Excellent [Member] | Agricultural real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	0	0
1 - Excellent [Member] | Agricultural other [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	0	0
2 - High quality [Member] | Total commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	21,677	18,660
2 - High quality [Member] | Commercial real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	11,359	7,397
2 - High quality [Member] | Commercial other [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	10,318	11,263
2 - High quality [Member] | Total agricultural [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	5,391	6,797
2 - High quality [Member] | Agricultural real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	3,963	4,647
2 - High quality [Member] | Agricultural other [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	1,428	2,150
3 - High satisfactory [Member] | Total commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	131,892	128,422
3 - High satisfactory [Member] | Commercial real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	100,031	99,136
3 - High satisfactory [Member] | Commercial other [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	31,861	29,286
3 - High satisfactory [Member] | Total agricultural [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	35,340	41,925
3 - High satisfactory [Member] | Agricultural real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	24,288	28,886
3 - High satisfactory [Member] | Agricultural other [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	11,052	13,039
4 - Low satisfactory [Member] | Total commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	333,592	285,418
4 - Low satisfactory [Member] | Commercial real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	257,872	222,431
4 - Low satisfactory [Member] | Commercial other [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	75,720	62,987
4 - Low satisfactory [Member] | Total agricultural [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	70,960	59,445
4 - Low satisfactory [Member] | Agricultural real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	46,446	37,279
4 - Low satisfactory [Member] | Agricultural other [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	24,514	22,166
5 - Special mention [Member] | Total commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	4,941	4,974
5 - Special mention [Member] | Commercial real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	4,464	4,501
5 - Special mention [Member] | Commercial other [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	477	473
5 - Special mention [Member] | Total agricultural [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	11,969	5,836
5 - Special mention [Member] | Agricultural real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	5,631	3,961
5 - Special mention [Member] | Agricultural other [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	6,338	1,875
6 - Substandard [Member] | Total commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	7,163	10,197
6 - Substandard [Member] | Commercial real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	6,936	9,941
6 - Substandard [Member] | Commercial other [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	227	256
6 - Substandard [Member] | Total agricultural [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	2,711	1,762
6 - Substandard [Member] | Agricultural real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	2,108	1,623
6 - Substandard [Member] | Agricultural other [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	603	139
7 - Vulnerable [Member] | Total commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	127	211
7 - Vulnerable [Member] | Commercial real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	127	211
7 - Vulnerable [Member] | Commercial other [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	0	0
7 - Vulnerable [Member] | Total agricultural [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	146	146
7 - Vulnerable [Member] | Agricultural real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	146	146
7 - Vulnerable [Member] | Agricultural other [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	0	0
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] | 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