Allowance for Credit Losses - Roll Forward Of the Allowance for Loan Losses (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023
Allowance for credit losses:
Beginning balance	$ 199,871	$ 194,391	$ 198,578	$ 192,090	$ 192,090
Charge-offs	(1,904)	(3,630)	(9,186)	(16,272)	(19,040)
Recoveries	1,201	1,697	2,838	5,706
Net (charge-offs) recoveries	(703)	(1,933)	(6,348)	(10,566)
Provision for (recovery of) credit losses on loans	1,210	5,315	8,148	16,275
Ending balance	200,378	197,773	200,378	197,773	198,578
Individually evaluated	13,953	13,657	13,953	13,657
Collectively evaluated	186,425	184,116	186,425	184,116
Loans:
Individually evaluated	71,631	53,723	71,631	53,723
Collectively evaluated	12,556,017	12,114,300	12,556,017	12,114,300
Loans, net of unearned income	12,627,648	12,168,023	12,627,648	12,168,023	12,351,230
Nonaccruing loans with no allowance for credit losses	32,620	24,845	32,620	24,845
Commercial, financial, agricultural
Allowance for credit losses:
Beginning balance	44,951	41,310	43,980	44,255	44,255
Charge-offs	(347)	(2,252)	(882)	(7,720)	(8,838)
Recoveries	514	690	1,385	2,689
Net (charge-offs) recoveries	167	(1,562)	503	(5,031)
Provision for (recovery of) credit losses on loans	(2,065)	4,696	(1,430)	5,246
Ending balance	43,053	44,444	43,053	44,444	43,980
Individually evaluated	8,805	11,194	8,805	11,194
Collectively evaluated	34,248	33,250	34,248	33,250
Loans:
Individually evaluated	15,370	20,996	15,370	20,996
Collectively evaluated	1,789,591	1,798,895	1,789,591	1,798,895
Loans, net of unearned income	1,804,961	1,819,891	1,804,961	1,819,891
Nonaccruing loans with no allowance for credit losses	122	1,987	122	1,987
Real estate – construction:
Allowance for credit losses:
Beginning balance	18,896	19,125	18,612	19,114	19,114
Charge-offs	0	0		(57)
Recoveries	0	48		48
Net (charge-offs) recoveries	0	48	0	(9)
Provision for (recovery of) credit losses on loans	(2,240)	483	(1,956)	551
Ending balance	16,656	19,656	16,656	19,656	18,612
Individually evaluated	0	0	0	0
Collectively evaluated	16,656	19,656	16,656	19,656
Loans:
Individually evaluated	241	0	241	0
Collectively evaluated	1,198,597	1,407,364	1,198,597	1,407,364
Loans, net of unearned income	1,198,838	1,407,364	1,198,838	1,407,364
Nonaccruing loans with no allowance for credit losses	0	0	0	0
Real estate – 1-4 family mortgage:
Allowance for credit losses:
Beginning balance	47,421	46,434	47,283	44,727	44,727
Charge-offs	(256)	(130)	(546)	(345)	(417)
Recoveries	57	181	130	375
Net (charge-offs) recoveries	(199)	51	(416)	30
Provision for (recovery of) credit losses on loans	(3)	(686)	352	1,042
Ending balance	47,219	45,799	47,219	45,799	47,283
Individually evaluated	0	77	0	77
Collectively evaluated	47,219	45,722	47,219	45,722
Loans:
Individually evaluated	7,815	13,007	7,815	13,007
Collectively evaluated	3,432,223	3,385,869	3,432,223	3,385,869
Loans, net of unearned income	3,440,038	3,398,876	3,440,038	3,398,876
Nonaccruing loans with no allowance for credit losses	6,868	11,441	6,868	11,441
Real estate – commercial mortgage:
Allowance for credit losses:
Beginning balance	77,125	75,667	77,020	71,798	71,798
Charge-offs	(10)	0	(5,737)	(5,512)	(5,568)
Recoveries	11	208	116	697
Net (charge-offs) recoveries	1	208	(5,621)	(4,815)
Provision for (recovery of) credit losses on loans	4,961	(642)	10,688	8,250
Ending balance	82,087	75,233	82,087	75,233	77,020
Individually evaluated	4,878	1,260	4,878	1,260
Collectively evaluated	77,209	73,973	77,209	73,973
Loans:
Individually evaluated	47,321	18,403	47,321	18,403
Collectively evaluated	5,947,831	5,294,763	5,947,831	5,294,763
Loans, net of unearned income	5,995,152	5,313,166	5,995,152	5,313,166
Nonaccruing loans with no allowance for credit losses	25,016	11,226	25,016	11,226
Lease financing
Allowance for credit losses:
Beginning balance	2,515	2,480	2,515	2,463	2,463
Charge-offs	(642)	(641)	(642)	(641)	(1,524)
Recoveries	8	2	26	13
Net (charge-offs) recoveries	(634)	(639)	(616)	(628)
Provision for (recovery of) credit losses on loans	503	1,514	485	1,520
Ending balance	2,384	3,355	2,384	3,355	2,515
Individually evaluated	0	856	0	856
Collectively evaluated	2,384	2,499	2,384	2,499
Loans:
Individually evaluated	614	1,047	614	1,047
Collectively evaluated	97,545	119,677	97,545	119,677
Loans, net of unearned income	98,159	120,724	98,159	120,724
Nonaccruing loans with no allowance for credit losses	614	191	614	191
Installment Loans to Individuals
Allowance for credit losses:
Beginning balance	8,963	9,375	9,168	9,733	9,733
Charge-offs	(649)	(607)	(1,379)	(1,997)	(2,636)
Recoveries	611	568	1,181	1,884
Net (charge-offs) recoveries	(38)	(39)	(198)	(113)
Provision for (recovery of) credit losses on loans	54	(50)	9	(334)
Ending balance	8,979	9,286	8,979	9,286	9,168
Individually evaluated	270	270	270	270
Collectively evaluated	8,709	9,016	8,709	9,016
Loans:
Individually evaluated	270	270	270	270
Collectively evaluated	90,230	107,732	90,230	107,732
Loans, net of unearned income	90,500	108,002	90,500	108,002
Nonaccruing loans with no allowance for credit losses	$ 0	$ 0	$ 0	0
Cumulative Effect, Period Of Adoption, Adjustment
Allowance for credit losses:
Beginning balance				(26)	(26)
Cumulative Effect, Period Of Adoption, Adjustment | Commercial, financial, agricultural
Allowance for credit losses:
Beginning balance				(26)	(26)
Cumulative Effect, Period Of Adoption, Adjustment | Real estate – construction:
Allowance for credit losses:
Beginning balance				0	0
Cumulative Effect, Period Of Adoption, Adjustment | Real estate – 1-4 family mortgage:
Allowance for credit losses:
Beginning balance				0	0
Cumulative Effect, Period Of Adoption, Adjustment | Real estate – commercial mortgage:
Allowance for credit losses:
Beginning balance				0	0
Cumulative Effect, Period Of Adoption, Adjustment | Lease financing
Allowance for credit losses:
Beginning balance				0	0
Cumulative Effect, Period Of Adoption, Adjustment | Installment Loans to Individuals
Allowance for credit losses:
Beginning balance				$ 0	$ 0