Loans and Allowance for Loan Losses - Allocation of ALL with Corresponding Percentage of ALL in Each Category to Total Loans, Net of Deferred Fee (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018	Dec. 31, 2017
Loans And Leases Receivable Disclosure [Line Items]
Allowance for loan and lease losses, Amount	$ 12,959	$ 12,113	$ 14,563	$ 13,721
Allowance for loan and lease losses, Percentage of total loans, net of deferred fees	0.88%	0.85%
Commercial real estate
Loans And Leases Receivable Disclosure [Line Items]
Allowance for loan and lease losses, Amount	$ 3,514	$ 3,309	3,512	3,324
Allowance for loan and lease losses, Percentage of total loans, net of deferred fees	0.24%	0.23%
Consumer real estate
Loans And Leases Receivable Disclosure [Line Items]
Allowance for loan and lease losses, Amount	$ 1,017	$ 1,005	1,036	1,063
Allowance for loan and lease losses, Percentage of total loans, net of deferred fees	0.07%	0.07%
Construction and land development
Loans And Leases Receivable Disclosure [Line Items]
Allowance for loan and lease losses, Amount	$ 2,366	$ 2,431	1,742	1,628
Allowance for loan and lease losses, Percentage of total loans, net of deferred fees	0.16%	0.17%
Commercial and industrial
Loans And Leases Receivable Disclosure [Line Items]
Allowance for loan and lease losses, Amount	$ 5,524	$ 5,036	7,798	7,209
Allowance for loan and lease losses, Percentage of total loans, net of deferred fees	0.38%	0.35%
Consumer
Loans And Leases Receivable Disclosure [Line Items]
Allowance for loan and lease losses, Amount	$ 139	$ 105	122	91
Allowance for loan and lease losses, Percentage of total loans, net of deferred fees	0.01%	0.01%
Other
Loans And Leases Receivable Disclosure [Line Items]
Allowance for loan and lease losses, Amount	$ 399	$ 227	$ 353	$ 406
Allowance for loan and lease losses, Percentage of total loans, net of deferred fees	0.03%	0.02%