Loans, Allowance for Loan Losses, and Credit Quality - Summary of loan composition (Details) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014	Jun. 30, 2014	Dec. 31, 2013
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 883,302	$ 883,341
Less allowance for loan losses	9,723	9,288
Loans, net	873,579	874,053
Loans Receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	883,302	883,341	$ 860,086
Less allowance for loan losses	9,723	9,288	9,642	$ 9,232
Loans, net	$ 873,579	$ 874,053	850,444
% of Total	100.00%	100.00%
Allowance for loan losses to loans	1.10%	1.05%
Loans Receivable | Commercial & industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 309,103	$ 289,379
Less allowance for loan losses	$ 3,553	$ 3,191	3,281	1,798
% of Total	35.00%	32.70%
Loans Receivable | Owner-occupied commercial real estate ("CRE")
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 175,809	$ 182,574
Less allowance for loan losses	$ 1,531	$ 1,230	1,096	766
% of Total	19.90%	20.70%
Loans Receivable | Agricultural ("AG") production
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 14,432	$ 14,617	13,982
Less allowance for loan losses	56	$ 53	44	18
Loans, net	$ 14,376		13,938
% of Total	1.60%	1.60%
Loans Receivable | AG real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 40,783	$ 42,754	41,934
Less allowance for loan losses	292	$ 226	272	59
Loans, net	$ 40,491		41,662
% of Total	4.60%	4.80%
Loans Receivable | CRE investment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 82,486	$ 81,873	79,639
Less allowance for loan losses	671	$ 511	575	505
Loans, net	$ 81,815		79,064
% of Total	9.30%	9.30%
Loans Receivable | Construction & land development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 38,387	$ 44,114	45,504
Less allowance for loan losses	2,046	$ 2,685	2,784	4,970
Loans, net	$ 36,341		42,720
% of Total	4.40%	5.00%
Loans Receivable | Residential construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 10,321	$ 11,333	11,895
Less allowance for loan losses	124	$ 140	167	229
Loans, net	$ 10,197		11,728
% of Total	1.20%	1.30%
Loans Receivable | Residential first mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 153,857	$ 158,683	154,713
Less allowance for loan losses	1,002	$ 866	833	544
Loans, net	$ 152,855		153,880
% of Total	17.40%	18.00%
Loans Receivable | Residential junior mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 52,433	$ 52,104	50,244
Less allowance for loan losses	399	$ 337	448	321
Loans, net	$ 52,034		49,796
% of Total	6.00%	5.90%
Loans Receivable | Retail & other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 5,691	$ 5,910	5,573
Less allowance for loan losses	49	$ 49	142	22
Loans, net	$ 5,642		5,431
% of Total	0.60%	0.70%
Loans Receivable | Originated
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 718,409	$ 701,706	647,476
Less allowance for loan losses	7,945	9,288	9,642	9,232
Loans, net	$ 710,464	$ 692,418	637,834
% of Total	100.00%	100.00%
Allowance for loan losses to loans	1.11%	1.32%
Loans Receivable | Originated | Commercial & industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 292,535	$ 268,654
Less allowance for loan losses	$ 2,866	$ 3,191	3,281	1,798
% of Total	40.70%	38.30%
Loans Receivable | Originated | Owner-occupied commercial real estate ("CRE")
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 138,081	$ 140,203
Less allowance for loan losses	$ 1,135	$ 1,230	1,096	766
% of Total	19.20%	20.00%
Loans Receivable | Originated | Agricultural ("AG") production
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 5,287	$ 5,580	4,653
Less allowance for loan losses	44	$ 53	44	18
Loans, net	$ 5,243		4,609
% of Total	0.70%	0.80%
Loans Receivable | Originated | AG real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 20,467	$ 20,060	18,189
Less allowance for loan losses	207	$ 226	272	59
Loans, net	$ 20,260		17,917
% of Total	2.80%	2.80%
Loans Receivable | Originated | CRE investment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 56,211	$ 53,339	50,929
Less allowance for loan losses	510	$ 511	575	505
Loans, net	$ 55,701		50,354
% of Total	7.80%	7.60%
Loans Receivable | Originated | Construction & land development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 28,662	$ 33,865	34,501
Less allowance for loan losses	1,974	$ 2,685	2,784	4,970
Loans, net	$ 26,688		31,717
% of Total	4.00%	4.80%
Loans Receivable | Originated | Residential construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 10,321	$ 11,333	11,895
Less allowance for loan losses	124	$ 140	167	229
Loans, net	$ 10,197		11,728
% of Total	1.40%	1.60%
Loans Receivable | Originated | Residential first mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 116,872	$ 119,866	110,084
Less allowance for loan losses	728	$ 866	833	544
Loans, net	$ 116,144		109,251
% of Total	16.30%	17.10%
Loans Receivable | Originated | Residential junior mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 44,629	$ 43,411	40,913
Less allowance for loan losses	318	$ 337	448	321
Loans, net	$ 44,311		40,465
% of Total	6.30%	6.20%
Loans Receivable | Originated | Retail & other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 5,344	$ 5,395	4,847
Less allowance for loan losses	39	$ 49	142	$ 22
Loans, net	$ 5,305		4,705
% of Total	0.80%	0.80%
Loans Receivable | Acquired
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 164,893	$ 181,635	212,610
Less allowance for loan losses	1,778
Loans, net	$ 163,115	$ 181,635
% of Total	100.00%	100.00%
Allowance for loan losses to loans	1.08%	0.00%
Loans Receivable | Acquired | Commercial & industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 16,568	$ 20,725
Less allowance for loan losses	$ 687
% of Total	10.00%	11.40%
Loans Receivable | Acquired | Owner-occupied commercial real estate ("CRE")
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 37,728	$ 42,371
Less allowance for loan losses	$ 396
% of Total	22.90%	23.30%
Loans Receivable | Acquired | Agricultural ("AG") production
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 9,145	$ 9,037	$ 9,329
Less allowance for loan losses	12
Loans, net	$ 9,133
% of Total	5.60%	5.00%
Loans Receivable | Acquired | AG real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 20,316	$ 22,694	$ 23,745
Less allowance for loan losses	85
Loans, net	$ 20,231
% of Total	12.30%	12.50%
Loans Receivable | Acquired | CRE investment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 26,275	$ 28,534	$ 28,710
Less allowance for loan losses	161
Loans, net	$ 26,114
% of Total	15.90%	15.70%
Loans Receivable | Acquired | Construction & land development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 9,725	$ 10,249	$ 11,003
Less allowance for loan losses	72
Loans, net	$ 9,653
% of Total	5.90%	5.60%
Loans Receivable | Acquired | Residential construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans
Less allowance for loan losses
Loans, net
% of Total
Loans Receivable | Acquired | Residential first mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 36,985	$ 38,817	$ 44,629
Less allowance for loan losses	274
Loans, net	$ 36,711
% of Total	22.50%	21.40%
Loans Receivable | Acquired | Residential junior mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 7,804	$ 8,693	$ 9,331
Less allowance for loan losses	81
Loans, net	$ 7,723
% of Total	4.70%	4.80%
Loans Receivable | Acquired | Retail & other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 347	$ 515	$ 726
Less allowance for loan losses	10
Loans, net	$ 337
% of Total	0.20%	0.30%