Loans and Allowance for Loan Losses - Summary of Risk Category of Loans by Class of Loans (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Accounts Notes And Loans Receivable [Line Items]
Total loans	$ 1,381,218	$ 1,249,074
Real Estate | Construction and Land Development
Accounts Notes And Loans Receivable [Line Items]
Total loans	110,710	91,908
Real Estate | Commercial Real Estate
Accounts Notes And Loans Receivable [Line Items]
Total loans	524,174	496,039
Real Estate | Single-family Residential Mortgages
Accounts Notes And Loans Receivable [Line Items]
Total loans	359,111	248,940
Commercial | Other
Accounts Notes And Loans Receivable [Line Items]
Total loans	299,817	280,766
Commercial | SBA
Accounts Notes And Loans Receivable [Line Items]
Total loans	87,406	131,421
Pass
Accounts Notes And Loans Receivable [Line Items]
Total loans	1,363,087	1,214,258
Pass | Real Estate | Construction and Land Development
Accounts Notes And Loans Receivable [Line Items]
Total loans	110,431	91,619
Pass | Real Estate | Commercial Real Estate
Accounts Notes And Loans Receivable [Line Items]
Total loans	515,034	469,422
Pass | Real Estate | Single-family Residential Mortgages
Accounts Notes And Loans Receivable [Line Items]
Total loans	358,350	248,940
Pass | Commercial | Other
Accounts Notes And Loans Receivable [Line Items]
Total loans	297,140	277,518
Pass | Commercial | SBA
Accounts Notes And Loans Receivable [Line Items]
Total loans	82,132	126,759
Special Mention
Accounts Notes And Loans Receivable [Line Items]
Total loans	5,352	23,208
Special Mention | Real Estate | Commercial Real Estate
Accounts Notes And Loans Receivable [Line Items]
Total loans	4,418	19,070
Special Mention | Commercial | Other
Accounts Notes And Loans Receivable [Line Items]
Total loans	934	2,360
Special Mention | Commercial | SBA
Accounts Notes And Loans Receivable [Line Items]
Total loans		1,778
Substandard
Accounts Notes And Loans Receivable [Line Items]
Total loans	6,193	9,033
Substandard | Real Estate | Commercial Real Estate
Accounts Notes And Loans Receivable [Line Items]
Total loans	1,682	5,416
Substandard | Commercial | Other
Accounts Notes And Loans Receivable [Line Items]
Total loans	1,743	888
Substandard | Commercial | SBA
Accounts Notes And Loans Receivable [Line Items]
Total loans	2,768	2,729
Impaired
Accounts Notes And Loans Receivable [Line Items]
Total loans	6,586	2,575
Impaired | Real Estate | Construction and Land Development
Accounts Notes And Loans Receivable [Line Items]
Total loans	279	289
Impaired | Real Estate | Commercial Real Estate
Accounts Notes And Loans Receivable [Line Items]
Total loans	3,040	2,131
Impaired | Real Estate | Single-family Residential Mortgages
Accounts Notes And Loans Receivable [Line Items]
Total loans	761
Impaired | Commercial | SBA
Accounts Notes And Loans Receivable [Line Items]
Total loans	$ 2,506	$ 155