Loans and Allowance for Loan Losses - Allocation of Allowance for Loan Losses by Loan Category Broken Out Between Loans Individually Evaluated for Impairment and Collectively Evaluated for Impairment (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016
Accounts Notes And Loans Receivable [Line Items]
Individually evaluated for impairment	$ 159	$ 191
Collectively evaluated for impairment	24,247	23,850
Ending balance	24,406	24,041	$ 22,898	$ 21,747
Commercial and Industrial
Accounts Notes And Loans Receivable [Line Items]
Individually evaluated for impairment	19	20
Collectively evaluated for impairment	4,559	4,441
Ending balance	4,578	4,461	5,402	5,309
Construction
Accounts Notes And Loans Receivable [Line Items]
Collectively evaluated for impairment	7,866	7,135
Ending balance	7,866	7,135	5,598	4,940
Residential Real Estate | 1-to-4 Family Mortgage
Accounts Notes And Loans Receivable [Line Items]
Individually evaluated for impairment	16	18
Collectively evaluated for impairment	3,106	3,179
Ending balance	3,122	3,197	2,896	3,197
Residential Real Estate | Residential Line of Credit
Accounts Notes And Loans Receivable [Line Items]
Collectively evaluated for impairment	1,165	944
Ending balance	1,165	944	1,514	1,613
Residential Real Estate | Multi-Family Mortgage
Accounts Notes And Loans Receivable [Line Items]
Collectively evaluated for impairment	449	434
Ending balance	449	434	508	504
Commercial Real Estate | Owner Occupied
Accounts Notes And Loans Receivable [Line Items]
Individually evaluated for impairment	95	120
Collectively evaluated for impairment	2,919	3,438
Ending balance	3,014	3,558	3,387	3,302
Commercial Real Estate | Non-Owner Occupied
Accounts Notes And Loans Receivable [Line Items]
Individually evaluated for impairment	29	33
Collectively evaluated for impairment	2,724	2,784
Ending balance	2,753	2,817	2,660	2,019
Consumer and Other
Accounts Notes And Loans Receivable [Line Items]
Collectively evaluated for impairment	1,459	1,495
Ending balance	$ 1,459	$ 1,495	$ 933	$ 863