Allowance for Loan Losses - Summary of Risk Grades of Portfolio by Class (Detail) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Financing Receivable Recorded Investment [Line Items]
Loans	$ 370,577	$ 356,871
Real Estate - Commercial [Member]
Financing Receivable Recorded Investment [Line Items]
Loans	134,120	114,712
Other Real Estate Construction [Member]
Financing Receivable Recorded Investment [Line Items]
Loans	32,457	40,186
Real Estate 1 - 4 Family Construction [Member]
Financing Receivable Recorded Investment [Line Items]
Loans	5,037	5,024
Real Estate - Residential [Member]
Financing Receivable Recorded Investment [Line Items]
Loans	78,373	77,919
Home Equity [Member]
Financing Receivable Recorded Investment [Line Items]
Loans	50,188	50,506
Other Loans [Member]
Financing Receivable Recorded Investment [Line Items]
Loans	2,879	2,838
Commercial Loan [Member]
Financing Receivable Recorded Investment [Line Items]
Loans	55,837	54,912
Consumer Loans [Member]
Financing Receivable Recorded Investment [Line Items]
Loans	11,686	10,774
Pass [Member]
Financing Receivable Recorded Investment [Line Items]
Loans	351,683	338,914
Pass [Member] | Real Estate - Commercial [Member]
Financing Receivable Recorded Investment [Line Items]
Loans	128,368	109,224
Pass [Member] | Other Real Estate Construction [Member]
Financing Receivable Recorded Investment [Line Items]
Loans	29,987	38,082
Pass [Member] | Real Estate 1 - 4 Family Construction [Member]
Financing Receivable Recorded Investment [Line Items]
Loans	5,037	5,024
Pass [Member] | Real Estate - Residential [Member]
Financing Receivable Recorded Investment [Line Items]
Loans	70,806	69,645
Pass [Member] | Home Equity [Member]
Financing Receivable Recorded Investment [Line Items]
Loans	49,066	49,743
Pass [Member] | Other Loans [Member]
Financing Receivable Recorded Investment [Line Items]
Loans	2,879	2,838
Pass [Member] | Commercial Loan [Member]
Financing Receivable Recorded Investment [Line Items]
Loans	53,939	53,649
Pass [Member] | Consumer Loans [Member]
Financing Receivable Recorded Investment [Line Items]
Loans	11,601	10,709
Watch [Member]
Financing Receivable Recorded Investment [Line Items]
Loans	15,285	14,172
Watch [Member] | Real Estate - Commercial [Member]
Financing Receivable Recorded Investment [Line Items]
Loans	3,765	3,321
Watch [Member] | Other Real Estate Construction [Member]
Financing Receivable Recorded Investment [Line Items]
Loans	2,081	1,713
Watch [Member] | Real Estate - Residential [Member]
Financing Receivable Recorded Investment [Line Items]
Loans	6,499	7,119
Watch [Member] | Home Equity [Member]
Financing Receivable Recorded Investment [Line Items]
Loans	970	740
Watch [Member] | Commercial Loan [Member]
Financing Receivable Recorded Investment [Line Items]
Loans	1,886	1,215
Watch [Member] | Consumer Loans [Member]
Financing Receivable Recorded Investment [Line Items]
Loans	84	64
Sub-standard [Member]
Financing Receivable Recorded Investment [Line Items]
Loans	3,609	3,785
Sub-standard [Member] | Real Estate - Commercial [Member]
Financing Receivable Recorded Investment [Line Items]
Loans	1,987	2,167
Sub-standard [Member] | Other Real Estate Construction [Member]
Financing Receivable Recorded Investment [Line Items]
Loans	389	391
Sub-standard [Member] | Real Estate - Residential [Member]
Financing Receivable Recorded Investment [Line Items]
Loans	1,068	1,155
Sub-standard [Member] | Home Equity [Member]
Financing Receivable Recorded Investment [Line Items]
Loans	152	23
Sub-standard [Member] | Commercial Loan [Member]
Financing Receivable Recorded Investment [Line Items]
Loans	12	48
Sub-standard [Member] | Consumer Loans [Member]
Financing Receivable Recorded Investment [Line Items]
Loans	$ 1	$ 1