Loans and Allowance for Loan Losses - Schedule of Non-Accrual Loans, Past Due Loans over 89 Days and Accruing and Troubled Debt Restructurings (TDR) by Class of Loans (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018	Dec. 31, 2017
Accounts Notes And Loans Receivable [Line Items]
Non-Accrual	$ 1,712	$ 2,078
Allowance for loan and lease losses, Amount	12,959	12,113	$ 14,563	$ 13,721
Troubled Debt Restructurings	1,255	1,391
Past Due Over 89 Days and Accruing		214
Commercial real estate
Accounts Notes And Loans Receivable [Line Items]
Allowance for loan and lease losses, Amount	3,514	3,309	3,512	3,324
Troubled Debt Restructurings	1,255	1,391
Consumer real estate
Accounts Notes And Loans Receivable [Line Items]
Non-Accrual	912	1,187
Allowance for loan and lease losses, Amount	1,017	1,005	1,036	1,063
Past Due Over 89 Days and Accruing		214
Construction and Land Development
Accounts Notes And Loans Receivable [Line Items]
Non-Accrual	8	19
Commercial and industrial
Accounts Notes And Loans Receivable [Line Items]
Non-Accrual	744	817
Allowance for loan and lease losses, Amount	5,524	5,036	7,798	7,209
Consumer
Accounts Notes And Loans Receivable [Line Items]
Non-Accrual	48	55
Allowance for loan and lease losses, Amount	$ 139	$ 105	$ 122	$ 91