Loans - Summary of Internal Risk Ratings of Loans (Detail) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable gross carrying amount	$ 327,512	$ 372,589
Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable gross carrying amount	186,021	191,645
Commercial Land Development [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable gross carrying amount	1,847	2,187
Commercial Other [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable gross carrying amount	34,646	30,508
Internal Credit Risk Rating [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable gross carrying amount	222,514	224,340
Internal Credit Risk Rating [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable gross carrying amount	186,021	191,645
Internal Credit Risk Rating [Member] | Commercial Land Development [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable gross carrying amount	1,847	2,187
Internal Credit Risk Rating [Member] | Commercial Other [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable gross carrying amount	34,646	30,508
Pass [Member] | Internal Credit Risk Rating [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable gross carrying amount	210,514	212,400
Pass [Member] | Internal Credit Risk Rating [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable gross carrying amount	179,624	186,303
Pass [Member] | Internal Credit Risk Rating [Member] | Commercial Land Development [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable gross carrying amount	197	158
Pass [Member] | Internal Credit Risk Rating [Member] | Commercial Other [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable gross carrying amount	30,693	25,939
Watch and Special Mention [Member] | Internal Credit Risk Rating [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable gross carrying amount	8,936	10,537
Watch and Special Mention [Member] | Internal Credit Risk Rating [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable gross carrying amount	4,812	4,403
Watch and Special Mention [Member] | Internal Credit Risk Rating [Member] | Commercial Land Development [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable gross carrying amount	1,650	1,726
Watch and Special Mention [Member] | Internal Credit Risk Rating [Member] | Commercial Other [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable gross carrying amount	2,474	4,408
Substandard [Member] | Internal Credit Risk Rating [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable gross carrying amount	3,064	1,403
Substandard [Member] | Internal Credit Risk Rating [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable gross carrying amount	1,585	939
Substandard [Member] | Internal Credit Risk Rating [Member] | Commercial Land Development [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable gross carrying amount		303
Substandard [Member] | Internal Credit Risk Rating [Member] | Commercial Other [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable gross carrying amount	$ 1,479	$ 161