Loans and Leases - Summary of Major Loan and Lease Categories (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases held for investment, originated	$ 4,140,503	$ 3,629,198
Total loans and leases held for investment, acquired	246,333	377,376
Total loans and leases held for investment	4,386,836	4,006,574
Imputed interest on lease financings, originated	(16,340)	(15,118)
Imputed interest on lease financings, acquired	0	0
Imputed interest on lease financings, included in the above table	(16,340)	(15,118)
Net deferred costs, originated	5,999	3,930
Net deferred costs, acquired	0	0
Net deferred costs, included in the above table	5,999	3,930
Overdraft deposits, originated	407	139
Overdraft deposits, acquired	0	0
Overdraft deposits	407	139
Commercial, Financial and Agricultural [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases held for investment, originated	939,564	913,166
Total loans and leases held for investment, acquired	7,465	24,519
Total loans and leases held for investment	947,029	937,685
Real Estate-Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases held for investment, originated	1,883,964	1,507,579
Total loans and leases held for investment, acquired	156,477	233,625
Total loans and leases held for investment	2,040,441	1,741,204
Real Estate-Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases held for investment, originated	232,595	215,513
Total loans and leases held for investment, acquired	0	0
Total loans and leases held for investment	232,595	215,513
Real Estate-Residential Secured for Business Purpose [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases held for investment, originated	339,349	302,393
Total loans and leases held for investment, acquired	34,624	60,403
Total loans and leases held for investment	373,973	362,796
Real Estate-Residential Secured for Personal Purpose [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases held for investment, originated	398,254	338,451
Total loans and leases held for investment, acquired	40,805	49,959
Total loans and leases held for investment	439,059	388,410
Real Estate-Home Equity Secured for Personal Purpose [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases held for investment, originated	167,612	177,523
Total loans and leases held for investment, acquired	6,823	8,728
Total loans and leases held for investment	174,435	186,251
Loans to Individuals [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases held for investment, originated	29,744	32,617
Total loans and leases held for investment, acquired	139	142
Total loans and leases held for investment	29,883	32,759
Lease Financings [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases held for investment, originated	149,421	141,956
Total loans and leases held for investment, acquired	0	0
Total loans and leases held for investment	$ 149,421	$ 141,956