Loans - Summary of Recorded Investment of Purchased Impaired Loans (Detail) - PCI Loans - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Financing Receivable, Impaired [Line Items]
30-89 Days Past Due	$ 390	$ 115
90 Days or More Past Due and Still Accruing	16	111
Nonaccruals	0	0
Total Past Due and Nonaccruals	406	226
Current	4,464	5,097
Total PCI Loans	4,870	5,323
Construction, land and land development
Financing Receivable, Impaired [Line Items]
30-89 Days Past Due		23
Nonaccruals	0	0
Total Past Due and Nonaccruals		23
Current	1,357	1,355
Total PCI Loans	1,357	1,378
Commercial mortgages (non-owner occupied)
Financing Receivable, Impaired [Line Items]
30-89 Days Past Due	126
Nonaccruals	0	0
Total Past Due and Nonaccruals	126
Current		142
Total PCI Loans	126	142
Commercial mortgages (owner occupied)
Financing Receivable, Impaired [Line Items]
30-89 Days Past Due	25
90 Days or More Past Due and Still Accruing		56
Nonaccruals	0	0
Total Past Due and Nonaccruals	25	56
Current	229	237
Total PCI Loans	254	293
Residential first mortgages
Financing Receivable, Impaired [Line Items]
30-89 Days Past Due	239	92
90 Days or More Past Due and Still Accruing	16	55
Nonaccruals	0	0
Total Past Due and Nonaccruals	255	147
Current	2,836	3,317
Total PCI Loans	3,091	3,464
Residential revolving and junior mortgages
Financing Receivable, Impaired [Line Items]
Nonaccruals	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
Nonaccruals	0	0
Total Past Due and Nonaccruals	0	0
Current	0	0
Total PCI Loans	0	0
Consumer
Financing Receivable, Impaired [Line Items]
Nonaccruals	0	0
Current	42	46
Total PCI Loans	$ 42	$ 46