Loans and Allowance For Loan Losses - Summary of Loan Portfolio Allocated by Management's Internal Risk Ratings (Detail) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Financing Receivable, Credit Quality Indicator [Line Items]
Credit Exposure	$ 968,945	$ 949,652
Commercial And Industrial [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Credit Exposure	416,308	389,746
Real Estate Construction And Land [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Credit Exposure	41,697	42,519
Real Estate HELOC [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Credit Exposure	995	982
Installment and Other [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Credit Exposure	13,180	13,476
Loans Receivable [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Credit Exposure	968,945	949,652
Loans Receivable [Member] | Pass [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Credit Exposure	937,761	925,736
Loans Receivable [Member] | Special Mention [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Credit Exposure	13,937	18,265
Loans Receivable [Member] | Substandard [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Credit Exposure	17,247	5,651
Loans Receivable [Member] | Commercial And Industrial [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Credit Exposure	416,308	389,746
Loans Receivable [Member] | Commercial And Industrial [Member] | Pass [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Credit Exposure	399,304	378,327
Loans Receivable [Member] | Commercial And Industrial [Member] | Special Mention [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Credit Exposure	7,254	6,894
Loans Receivable [Member] | Commercial And Industrial [Member] | Substandard [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Credit Exposure	9,750	4,525
Loans Receivable [Member] | Real Estate Construction And Land [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Credit Exposure	41,697	42,519
Loans Receivable [Member] | Real Estate Construction And Land [Member] | Pass [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Credit Exposure	39,919	40,731
Loans Receivable [Member] | Real Estate Construction And Land [Member] | Special Mention [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Credit Exposure		1,788
Loans Receivable [Member] | Real Estate Construction And Land [Member] | Substandard [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Credit Exposure	1,778
Loans Receivable [Member] | Real Estate, Other [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Credit Exposure	496,765	502,929
Loans Receivable [Member] | Real Estate, Other [Member] | Pass [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Credit Exposure	486,959	494,314
Loans Receivable [Member] | Real Estate, Other [Member] | Special Mention [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Credit Exposure	5,188	7,928
Loans Receivable [Member] | Real Estate, Other [Member] | Substandard [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Credit Exposure	4,618	687
Loans Receivable [Member] | Real Estate HELOC [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Credit Exposure	995	982
Loans Receivable [Member] | Real Estate HELOC [Member] | Pass [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Credit Exposure	995	982
Loans Receivable [Member] | Installment and Other [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Credit Exposure	13,180	13,476
Loans Receivable [Member] | Installment and Other [Member] | Pass [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Credit Exposure	10,584	11,382
Loans Receivable [Member] | Installment and Other [Member] | Special Mention [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Credit Exposure	1,495	1,655
Loans Receivable [Member] | Installment and Other [Member] | Substandard [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Credit Exposure	$ 1,101	$ 439