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	Sep. 30, 2018	Jun. 30, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Dec. 31, 2016
Accounts Notes And Loans Receivable [Line Items]
Individually evaluated for impairment	$ 416		$ 191
Collectively evaluated for impairment	26,581		23,850
Acquired with deteriorated credit quality	611
Ending balance	27,608	$ 26,347	24,041	$ 23,482	$ 23,247	$ 21,747
Commercial and Industrial
Accounts Notes And Loans Receivable [Line Items]
Individually evaluated for impairment	350		20
Collectively evaluated for impairment	5,002		4,441
Acquired with deteriorated credit quality	13
Ending balance	5,365	4,747	4,461	5,734	5,440	5,309
Construction
Accounts Notes And Loans Receivable [Line Items]
Collectively evaluated for impairment	8,196		7,135
Acquired with deteriorated credit quality	72
Ending balance	8,268	9,023	7,135	6,125	5,579	4,940
Residential Real Estate | 1-to-4 Family Mortgage
Accounts Notes And Loans Receivable [Line Items]
Individually evaluated for impairment	8		18
Collectively evaluated for impairment	3,401		3,179
Acquired with deteriorated credit quality	111
Ending balance	3,520	3,378	3,197	2,759	2,974	3,197
Residential Real Estate | Residential Line of Credit
Accounts Notes And Loans Receivable [Line Items]
Collectively evaluated for impairment	838		944
Ending balance	838	795	944	1,028	1,445	1,613
Residential Real Estate | Multi-Family Mortgage
Accounts Notes And Loans Receivable [Line Items]
Collectively evaluated for impairment	683		434
Ending balance	683	391	434	523	513	504
Commercial Real Estate | Owner Occupied
Accounts Notes And Loans Receivable [Line Items]
Individually evaluated for impairment	58		120
Collectively evaluated for impairment	3,410		3,438
Acquired with deteriorated credit quality	13
Ending balance	3,481	3,290	3,558	4,008	3,983	3,302
Commercial Real Estate | Non-Owner Occupied
Accounts Notes And Loans Receivable [Line Items]
Individually evaluated for impairment			33
Collectively evaluated for impairment	3,544		2,784
Acquired with deteriorated credit quality	367
Ending balance	3,911	3,272	2,817	2,477	2,452	2,019
Consumer and Other
Accounts Notes And Loans Receivable [Line Items]
Collectively evaluated for impairment	1,507		1,495
Acquired with deteriorated credit quality	35
Ending balance	$ 1,542	$ 1,451	$ 1,495	$ 828	$ 861	$ 863