Loans - Summary of Recorded Investment of Purchased Impaired Loans (Detail) - PCI Loans - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Financing Receivable, Impaired [Line Items]
30-89 Days Past Due	$ 46	$ 115
90 Days or More Past Due and Still Accruing	156	111
Nonaccrual	0	0
Total Past Due and Nonaccrual	202	226
Current	4,896	5,097
Total PCI Loans	5,098	5,323
Construction, land and land development
Financing Receivable, Impaired [Line Items]
30-89 Days Past Due	16	23
Nonaccrual	0	0
Total Past Due and Nonaccrual	16	23
Current	1,360	1,355
Total PCI Loans	1,376	1,378
Commercial mortgages (non-owner occupied)
Financing Receivable, Impaired [Line Items]
Nonaccrual	0	0
Current	129	142
Total PCI Loans	129	142
Commercial mortgages (owner occupied)
Financing Receivable, Impaired [Line Items]
90 Days or More Past Due and Still Accruing		56
Nonaccrual	0	0
Total Past Due and Nonaccrual		56
Current	274	237
Total PCI Loans	274	293
Residential first mortgages
Financing Receivable, Impaired [Line Items]
30-89 Days Past Due	30	92
90 Days or More Past Due and Still Accruing	156	55
Nonaccrual	0	0
Total Past Due and Nonaccrual	186	147
Current	3,088	3,317
Total PCI Loans	3,274	3,464
Residential revolving and junior mortgages
Financing Receivable, Impaired [Line Items]
Nonaccrual	0	0
Commercial and industrial
Financing Receivable, Impaired [Line Items]
30-89 Days Past Due	0	0
90 Days or More Past Due and Still Accruing	0	0
Nonaccrual	0	0
Total Past Due and Nonaccrual	0	0
Current	0	0
Total PCI Loans	0	0
Consumer
Financing Receivable, Impaired [Line Items]
Nonaccrual	0	0
Current	45	46
Total PCI Loans	$ 45	$ 46