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	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Accounts Notes And Loans Receivable [Line Items]
Individually evaluated for impairment	$ 191	$ 513	$ 973
Collectively evaluated for impairment	23,850	21,234	23,487
Ending balance	24,041	21,747	24,460	$ 29,030
Commercial and Industrial
Accounts Notes And Loans Receivable [Line Items]
Individually evaluated for impairment	20	135	89
Collectively evaluated for impairment	4,441	5,174	5,046
Ending balance	4,461	5,309	5,135	6,600
Construction
Accounts Notes And Loans Receivable [Line Items]
Individually evaluated for impairment			5
Collectively evaluated for impairment	7,135	4,940	5,138
Ending balance	7,135	4,940	5,143	3,721
Residential Real Estate | 1-to-4 Family Mortgage
Accounts Notes And Loans Receivable [Line Items]
Individually evaluated for impairment	18	23	66
Collectively evaluated for impairment	3,179	3,174	4,110
Ending balance	3,197	3,197	4,176	6,364
Residential Real Estate | Residential Line of Credit
Accounts Notes And Loans Receivable [Line Items]
Collectively evaluated for impairment	944	1,613	2,201
Ending balance	944	1,613	2,201	2,790
Residential Real Estate | Multi-Family Mortgage
Accounts Notes And Loans Receivable [Line Items]
Collectively evaluated for impairment	434	504	311
Ending balance	434	504	311	184
Commercial Real Estate | Owner Occupied
Accounts Notes And Loans Receivable [Line Items]
Individually evaluated for impairment	120	113	74
Collectively evaluated for impairment	3,438	3,189	3,608
Ending balance	3,558	3,302	3,682	6,075
Commercial Real Estate | Non-Owner Occupied
Accounts Notes And Loans Receivable [Line Items]
Individually evaluated for impairment	33	242	739
Collectively evaluated for impairment	2,784	1,777	1,883
Ending balance	2,817	2,019	2,622	2,641
Consumer and Other
Accounts Notes And Loans Receivable [Line Items]
Collectively evaluated for impairment	1,495	863	1,190
Ending balance	$ 1,495	$ 863	$ 1,190	$ 655