Loans and Leases - Allowance for Credit Losses, Loans and Leases Roll Forward (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	$ 79,004	$ 71,924	$ 83,044
(Reversal of provision) provision for credit losses	11,780	10,975	(10,907)
Charge-offs	(6,186)	(4,669)	(3,013)
Recoveries	789	774	2,800
Ending balance	85,387	79,004	71,924
Commercial, Financial and Agricultural [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	16,920	13,538	13,584
(Reversal of provision) provision for credit losses	1,289	3,705	(30)
Charge-offs	(4,877)	(887)	(1,641)
Recoveries	367	564	1,625
Ending balance	13,699	16,920	13,538
Real Estate-Commercial [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	41,673	41,095	52,230
(Reversal of provision) provision for credit losses	4,213	3,854	(11,339)
Charge-offs	(50)	(3,282)	(594)
Recoveries	13	6	798
Ending balance	45,849	41,673	41,095
Real Estate-Construction [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	4,952	4,575	3,298
(Reversal of provision) provision for credit losses	1,797	377	1,277
Charge-offs	(207)	0	0
Recoveries	1	0	0
Ending balance	6,543	4,952	4,575
Real Estate-Residential Secured for Business Purpose [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	7,054	6,482	7,317
(Reversal of provision) provision for credit losses	1,503	517	(688)
Charge-offs	(50)	0	(227)
Recoveries	185	55	80
Ending balance	8,692	7,054	6,482
Real Estate-Residential Secured for Personal Purpose [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	3,685	2,403	3,055
(Reversal of provision) provision for credit losses	2,664	1,282	(652)
Charge-offs	0	0	0
Recoveries	0	0	0
Ending balance	6,349	3,685	2,403
Real Estate-Home Equity Secured for Personal Purpose [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	1,287	1,028	1,176
(Reversal of provision) provision for credit losses	4	221	(212)
Charge-offs	(85)	0	0
Recoveries	83	38	64
Ending balance	1,289	1,287	1,028
Loans to Individuals [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	351	363	533
(Reversal of provision) provision for credit losses	467	167	(35)
Charge-offs	(507)	(255)	(240)
Recoveries	81	76	105
Ending balance	392	351	363
Lease Financings [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	3,082	2,290	1,701
(Reversal of provision) provision for credit losses	(157)	1,002	772
Charge-offs	(410)	(245)	(311)
Recoveries	59	35	128
Ending balance	2,574	3,082	2,290
Unallocated [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	$ 0	150	150
(Reversal of provision) provision for credit losses		(150)	0
Ending balance		$ 0	$ 150