Loans and Allowance for Credit Losses - Loan Portfolio by Risk Rating (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Financing Receivable, Recorded Investment
Loans	$ 777,717	$ 755,361
Pass
Financing Receivable, Recorded Investment
Loans	706,852	675,986
Special Mention
Financing Receivable, Recorded Investment
Loans	21,396	29,911
Substandard
Financing Receivable, Recorded Investment
Loans	49,469	49,464
Doubtful
Financing Receivable, Recorded Investment
Loans	0	0
Commercial
Financing Receivable, Recorded Investment
Loans	108,585	114,161
Commercial | Commercial and industrial
Financing Receivable, Recorded Investment
Loans	90,511	88,652
Commercial | Commercial and industrial | Pass
Financing Receivable, Recorded Investment
Loans	74,450	75,212
Commercial | Commercial and industrial | Special Mention
Financing Receivable, Recorded Investment
Loans	8,692	907
Commercial | Commercial and industrial | Substandard
Financing Receivable, Recorded Investment
Loans	7,369	12,533
Commercial | Commercial and industrial | Doubtful
Financing Receivable, Recorded Investment
Loans	0	0
Commercial | Agricultural land and production
Financing Receivable, Recorded Investment
Loans	18,074	25,509
Commercial | Agricultural land and production | Pass
Financing Receivable, Recorded Investment
Loans	9,036	16,562
Commercial | Agricultural land and production | Special Mention
Financing Receivable, Recorded Investment
Loans	1,986	8,681
Commercial | Agricultural land and production | Substandard
Financing Receivable, Recorded Investment
Loans	7,052	266
Commercial | Agricultural land and production | Doubtful
Financing Receivable, Recorded Investment
Loans	0	0
Real Estate
Financing Receivable, Recorded Investment
Loans	579,715	550,796
Real Estate | Owner occupied
Financing Receivable, Recorded Investment
Loans	191,918	191,665
Real Estate | Owner occupied | Pass
Financing Receivable, Recorded Investment
Loans	184,377	184,987
Real Estate | Owner occupied | Special Mention
Financing Receivable, Recorded Investment
Loans	4,700	2,865
Real Estate | Owner occupied | Substandard
Financing Receivable, Recorded Investment
Loans	2,841	3,813
Real Estate | Owner occupied | Doubtful
Financing Receivable, Recorded Investment
Loans	0	0
Real Estate | Real estate construction and other land loans
Financing Receivable, Recorded Investment
Loans	84,135	69,200
Real Estate | Real estate construction and other land loans | Pass
Financing Receivable, Recorded Investment
Loans	80,504	62,538
Real Estate | Real estate construction and other land loans | Special Mention
Financing Receivable, Recorded Investment
Loans	1,783	5,259
Real Estate | Real estate construction and other land loans | Substandard
Financing Receivable, Recorded Investment
Loans	1,848	1,403
Real Estate | Real estate construction and other land loans | Doubtful
Financing Receivable, Recorded Investment
Loans	0	0
Real Estate | Commercial real estate
Financing Receivable, Recorded Investment
Loans	212,008	184,225
Real Estate | Commercial real estate | Pass
Financing Receivable, Recorded Investment
Loans	207,673	179,966
Real Estate | Commercial real estate | Special Mention
Financing Receivable, Recorded Investment
Loans	2,438	1,548
Real Estate | Commercial real estate | Substandard
Financing Receivable, Recorded Investment
Loans	1,897	2,711
Real Estate | Commercial real estate | Doubtful
Financing Receivable, Recorded Investment
Loans	0	0
Real Estate | Agricultural real estate
Financing Receivable, Recorded Investment
Loans	72,082	86,761
Real Estate | Agricultural real estate | Pass
Financing Receivable, Recorded Investment
Loans	43,136	49,270
Real Estate | Agricultural real estate | Special Mention
Financing Receivable, Recorded Investment
Loans	1,290	10,390
Real Estate | Agricultural real estate | Substandard
Financing Receivable, Recorded Investment
Loans	27,656	27,101
Real Estate | Agricultural real estate | Doubtful
Financing Receivable, Recorded Investment
Loans	0	0
Real Estate | Other real estate
Financing Receivable, Recorded Investment
Loans	19,572	18,945
Real Estate | Other real estate | Pass
Financing Receivable, Recorded Investment
Loans	19,572	18,779
Real Estate | Other real estate | Special Mention
Financing Receivable, Recorded Investment
Loans	0	166
Real Estate | Other real estate | Substandard
Financing Receivable, Recorded Investment
Loans	0	0
Real Estate | Other real estate | Doubtful
Financing Receivable, Recorded Investment
Loans	0	0
Consumer
Financing Receivable, Recorded Investment
Loans	89,417	90,404
Consumer | Equity loans and lines of credit
Financing Receivable, Recorded Investment
Loans	61,822	64,494
Consumer | Equity loans and lines of credit | Pass
Financing Receivable, Recorded Investment
Loans	60,512	62,782
Consumer | Equity loans and lines of credit | Special Mention
Financing Receivable, Recorded Investment
Loans	507	95
Consumer | Equity loans and lines of credit | Substandard
Financing Receivable, Recorded Investment
Loans	803	1,617
Consumer | Equity loans and lines of credit | Doubtful
Financing Receivable, Recorded Investment
Loans	0	0
Consumer | Consumer and installment
Financing Receivable, Recorded Investment
Loans	27,595	25,910
Consumer | Consumer and installment | Pass
Financing Receivable, Recorded Investment
Loans	27,592	25,890
Consumer | Consumer and installment | Special Mention
Financing Receivable, Recorded Investment
Loans	0	0
Consumer | Consumer and installment | Substandard
Financing Receivable, Recorded Investment
Loans	3	20
Consumer | Consumer and installment | Doubtful
Financing Receivable, Recorded Investment
Loans	$ 0	$ 0