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, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024	Dec. 31, 2024
Allowance for credit losses:
Beginning balance	$ 290,770	$ 199,871	$ 201,756	$ 198,578	$ 198,578
Charge-offs	(5,054)	(1,904)	(19,162)	(9,186)	(13,809)
Recoveries	715	1,201	2,894	2,838
Net charge-offs	(4,339)	(703)	(16,268)	(6,348)
Provision for (recovery of) credit losses on loans	9,650	1,210	87,100	8,148
Ending balance	297,591	200,378	297,591	200,378	201,756
Nonaccruing loans with no allowance for credit losses	51,208	32,650	51,208	32,650
Cumulative Effect, Period Of Adoption, Adjustment
Allowance for credit losses:
Beginning balance	1,510		25,003
Ending balance					25,003
Commercial, financial, agricultural
Allowance for credit losses:
Beginning balance	59,676	44,951	38,527	43,980	43,980
Charge-offs	(2,557)	(347)	(8,474)	(882)	(4,463)
Recoveries	51	514	1,636	1,385
Net charge-offs	(2,506)	167	(6,838)	503
Provision for (recovery of) credit losses on loans	1,466	(2,065)	19,807	(1,430)
Ending balance	60,526	43,053	60,526	43,053	38,527
Nonaccruing loans with no allowance for credit losses	25,041	122	25,041	122
Commercial, financial, agricultural | Cumulative Effect, Period Of Adoption, Adjustment
Allowance for credit losses:
Beginning balance	1,890		9,030
Ending balance					9,030
Real estate – construction:
Allowance for credit losses:
Beginning balance	21,784	18,896	15,126	18,612	18,612
Charge-offs	(8)	0	(113)	0
Recoveries	6	0	6	0
Net charge-offs	(2)	0	(107)	0
Provision for (recovery of) credit losses on loans	2,171	(2,240)	6,937	(1,956)
Ending balance	23,953	16,656	23,953	16,656	15,126
Nonaccruing loans with no allowance for credit losses	4,412	0	4,412	0
Real estate – construction: | Cumulative Effect, Period Of Adoption, Adjustment
Allowance for credit losses:
Beginning balance	0		1,997
Ending balance					1,997
Real estate – 1-4 family mortgage:
Allowance for credit losses:
Beginning balance	65,703	47,421	47,761	47,283	47,283
Charge-offs	(612)	(256)	(1,240)	(546)	(966)
Recoveries	84	57	154	130
Net charge-offs	(528)	(199)	(1,086)	(416)
Provision for (recovery of) credit losses on loans	1,146	(3)	19,382	352
Ending balance	66,826	47,219	66,826	47,219	47,761
Nonaccruing loans with no allowance for credit losses	4,275	6,898	4,275	6,898
Real estate – 1-4 family mortgage: | Cumulative Effect, Period Of Adoption, Adjustment
Allowance for credit losses:
Beginning balance	505		769
Ending balance					769
Real estate – commercial mortgage:
Allowance for credit losses:
Beginning balance	135,572	77,125	90,204	77,020	77,020
Charge-offs	(1,296)	(10)	(5,701)	(5,737)	(5,737)
Recoveries	429	11	551	116
Net charge-offs	(867)	1	(5,150)	(5,621)
Provision for (recovery of) credit losses on loans	5,522	4,961	41,083	10,688
Ending balance	139,342	82,087	139,342	82,087	90,204
Nonaccruing loans with no allowance for credit losses	17,480	25,016	17,480	25,016
Real estate – commercial mortgage: | Cumulative Effect, Period Of Adoption, Adjustment
Allowance for credit losses:
Beginning balance	(885)		13,205
Ending balance					13,205
Lease financing
Allowance for credit losses:
Beginning balance	1,935	2,515	3,368	2,515	2,515
Charge-offs	(42)	(642)	(2,436)	(642)	(642)
Recoveries	90	8	103	26
Net charge-offs	48	(634)	(2,333)	(616)
Provision for (recovery of) credit losses on loans	(503)	503	445	485
Ending balance	1,480	2,384	1,480	2,384	3,368
Nonaccruing loans with no allowance for credit losses	0	614	0	614
Lease financing | Cumulative Effect, Period Of Adoption, Adjustment
Allowance for credit losses:
Beginning balance	0		0
Ending balance					0
Installment Loans to Individuals
Allowance for credit losses:
Beginning balance	6,100	8,963	6,770	9,168	9,168
Charge-offs	(539)	(649)	(1,198)	(1,379)	(1,856)
Recoveries	55	611	444	1,181
Net charge-offs	(484)	(38)	(754)	(198)
Provision for (recovery of) credit losses on loans	(152)	54	(554)	9
Ending balance	5,464	8,979	5,464	8,979	6,770
Nonaccruing loans with no allowance for credit losses	0	$ 0	0	$ 0
Installment Loans to Individuals | Cumulative Effect, Period Of Adoption, Adjustment
Allowance for credit losses:
Beginning balance	$ 0		$ 2
Ending balance					$ 2