Allowance for Credit Losses - Roll Forward Of the Allowance for Loan Losses (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2025	Mar. 31, 2024	Dec. 31, 2024
Allowance for credit losses:
Beginning balance	$ 201,756	$ 198,578	$ 198,578
Charge-offs	(1,129)	(910)	(13,809)
Recoveries	1,254	746
Net recoveries (charge-offs)	125	(164)
(Recovery of) provision for credit losses on loans	2,050	2,638
Ending balance	203,931	201,052	201,756
Individually evaluated	15,767	9,947
Collectively evaluated	188,164	191,105
Loans:
Individually evaluated	73,125	36,491
Collectively evaluated	12,982,468	12,464,034
Loans, net of unearned income	13,055,593	12,500,525	12,885,020
Nonaccruing loans with no allowance for credit losses	21,561	17,615
Commercial, financial, agricultural
Allowance for credit losses:
Beginning balance	38,527	43,980	43,980
Charge-offs	(94)	(349)	(4,463)
Recoveries	958	346
Net recoveries (charge-offs)	864	(3)
(Recovery of) provision for credit losses on loans	(950)	1,944
Ending balance	38,441	45,921	38,527
Individually evaluated	4,522	9,104
Collectively evaluated	33,919	36,817
Loans:
Individually evaluated	11,132	15,861
Collectively evaluated	1,877,448	1,853,547
Loans, net of unearned income	1,888,580	1,869,408
Nonaccruing loans with no allowance for credit losses	122	157
Real estate – construction:
Allowance for credit losses:
Beginning balance	15,126	18,612	18,612
Charge-offs	0	0
Recoveries	0	0
Net recoveries (charge-offs)	0	0
(Recovery of) provision for credit losses on loans	1,435	(1,295)
Ending balance	16,561	17,317	15,126
Individually evaluated	0	0
Collectively evaluated	16,561	17,317
Loans:
Individually evaluated	2,434	0
Collectively evaluated	1,088,428	1,243,535
Loans, net of unearned income	1,090,862	1,243,535
Nonaccruing loans with no allowance for credit losses	2,434	0
Real estate – 1-4 family mortgage:
Allowance for credit losses:
Beginning balance	47,761	47,283	47,283
Charge-offs	(309)	(82)	(966)
Recoveries	33	48
Net recoveries (charge-offs)	(276)	(34)
(Recovery of) provision for credit losses on loans	3,226	317
Ending balance	50,711	47,566	47,761
Individually evaluated	0	0
Collectively evaluated	50,711	47,566
Loans:
Individually evaluated	8,750	7,327
Collectively evaluated	3,574,330	3,421,959
Loans, net of unearned income	3,583,080	3,429,286
Nonaccruing loans with no allowance for credit losses	6,418	7,328
Real estate – commercial mortgage:
Allowance for credit losses:
Beginning balance	90,204	77,020	77,020
Charge-offs	(461)	0	(5,737)
Recoveries	6	6
Net recoveries (charge-offs)	(455)	6
(Recovery of) provision for credit losses on loans	(1,669)	1,699
Ending balance	88,080	78,725	90,204
Individually evaluated	8,922	573
Collectively evaluated	79,158	78,152
Loans:
Individually evaluated	46,593	13,033
Collectively evaluated	6,273,527	5,740,197
Loans, net of unearned income	6,320,120	5,753,230
Nonaccruing loans with no allowance for credit losses	11,998	10,130
Lease financing
Allowance for credit losses:
Beginning balance	3,368	2,515	2,515
Charge-offs	0	0	(642)
Recoveries	9	8
Net recoveries (charge-offs)	9	8
(Recovery of) provision for credit losses on loans	267	31
Ending balance	3,644	2,554	3,368
Individually evaluated	2,053	0
Collectively evaluated	1,591	2,554
Loans:
Individually evaluated	3,946	0
Collectively evaluated	81,466	107,474
Loans, net of unearned income	85,412	107,474
Nonaccruing loans with no allowance for credit losses	589	0
Installment Loans to Individuals
Allowance for credit losses:
Beginning balance	6,770	9,168	9,168
Charge-offs	(265)	(479)	(1,856)
Recoveries	248	338
Net recoveries (charge-offs)	(17)	(141)
(Recovery of) provision for credit losses on loans	(259)	(58)
Ending balance	6,494	8,969	$ 6,770
Individually evaluated	270	270
Collectively evaluated	6,224	8,699
Loans:
Individually evaluated	270	270
Collectively evaluated	87,269	97,322
Loans, net of unearned income	87,539	97,592
Nonaccruing loans with no allowance for credit losses	$ 0	$ 0