Loans - Summary of Internal Risk Ratings of Loans (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable gross carrying amount	$ 372,589	$ 333,710
Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable gross carrying amount	191,645	156,991
Commercial Land development [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable gross carrying amount	2,187	2,687
Commercial Other [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable gross carrying amount	30,508	19,715
Internal Credit Risk Rating [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable gross carrying amount	224,340	179,393
Internal Credit Risk Rating [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable gross carrying amount	191,645	156,991
Internal Credit Risk Rating [Member] | Commercial Land development [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable gross carrying amount	2,187	2,687
Internal Credit Risk Rating [Member] | Commercial Other [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable gross carrying amount	30,508	19,715
Pass [Member] | Internal Credit Risk Rating [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable gross carrying amount	212,400	161,652
Pass [Member] | Internal Credit Risk Rating [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable gross carrying amount	186,303	144,763
Pass [Member] | Internal Credit Risk Rating [Member] | Commercial Land development [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable gross carrying amount	158	2,384
Pass [Member] | Internal Credit Risk Rating [Member] | Commercial Other [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable gross carrying amount	25,939	14,505
Watch and Special Mention [Member] | Internal Credit Risk Rating [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable gross carrying amount	10,537	14,964
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	4,403	9,786
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	1,726
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	4,408	5,178
Substandard [Member] | Internal Credit Risk Rating [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable gross carrying amount	1,403	2,777
Substandard [Member] | Internal Credit Risk Rating [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable gross carrying amount	939	2,442
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	303
Substandard [Member] | Internal Credit Risk Rating [Member] | Commercial Other [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable gross carrying amount	$ 161	$ 32