Loans (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans	$ 1,336,125	$ 1,164,821
Net deferred loan (fees) costs	463	(176)
Overdraft deposits	114	128
Outstanding principal balance and the carrying amount of loan acquired [Abstract]
Outstanding principal balance	79,523	104,172
Carrying amount	73,796	96,487
Outstanding principal balance and the carrying amount of loan acquired, impaired [Abstract]
Outstanding principal balance	27,876	34,378
Carrying amount	23,430	28,669
Changes in the accretable discount on acquired loans [Abstract]
Balance at January 1	6,103	7,299	$ 1,440
Additions from merger with MainStreet	0	0	7,140
Accretion	(3,117)	(3,232)	(4,313)
Reclassification from nonaccretable difference	1,006	2,197	238
Other changes, net	898	(161)	2,794
Balance at December 31	4,890	6,103	$ 7,299
Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans	251,666	208,717
Commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans	760,848	625,218
Commercial real estate | Construction and land development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans	123,147	114,258
Commercial real estate | Real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans	637,701	510,960
Residential real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans	319,183	325,855
Residential real estate | Real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans	209,326	215,104
Residential real estate | Home equity
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans	109,857	110,751
Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans	$ 4,428	$ 5,031