Allowance for Credit Losses - Roll Forward Of the Allowance for Loan Losses (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021	Dec. 31, 2021
Allowance for loan losses:
Beginning balance	$ 166,131	$ 172,354	$ 164,171	$ 176,144
Charge-offs	(3,259)	(2,979)	(10,274)	(11,203)
Recoveries	1,684	1,863	5,511	6,297
Net (charge-offs) recoveries	(1,575)	(1,116)	(4,763)	(4,906)
Provision for (recovery of provision for) credit losses on loans	9,800	(1,200)	13,300	(1,200)
Ending balance	174,356	170,038	174,356	170,038
Individually evaluated	7,083	16,498	7,083	16,498
Collectively evaluated	167,273	153,540	167,273	153,540
Loans:
Individually evaluated	34,619	40,241	34,619	40,241
Collectively evaluated	11,070,385	9,976,583	11,070,385	9,976,583
Loans, net of unearned income	11,105,004	10,016,824	11,105,004	10,016,824	$ 10,020,914
Nonaccruing loans with no allowance for credit losses	11,026	8,572	11,026	8,572
Commercial, financial, agricultural
Allowance for loan losses:
Beginning balance	30,193	36,994	33,922	39,031
Charge-offs	(373)	(1,225)	(4,714)	(5,907)
Recoveries	415	418	1,982	940
Net (charge-offs) recoveries	42	(807)	(2,732)	(4,967)
Provision for (recovery of provision for) credit losses on loans	268	(1,210)	(2,335)	913
Ending balance	30,503	34,977	30,503	34,977
Individually evaluated	4,064	9,717	4,064	9,717
Collectively evaluated	26,439	25,260	26,439	25,260
Loans:
Individually evaluated	9,088	15,193	9,088	15,193
Collectively evaluated	1,504,003	1,420,826	1,504,003	1,420,826
Loans, net of unearned income	1,513,091	1,436,019	1,513,091	1,436,019
Nonaccruing loans with no allowance for credit losses	429	2,658	429	2,658
Real estate – construction:
Allowance for loan losses:
Beginning balance	17,290	15,729	16,419	16,047
Charge-offs	0	0	0	(52)
Recoveries	0	0	0	13
Net (charge-offs) recoveries	0	0	0	(39)
Provision for (recovery of provision for) credit losses on loans	1,454	440	2,325	161
Ending balance	18,744	16,169	18,744	16,169
Individually evaluated	0	0	0	0
Collectively evaluated	18,744	16,169	18,744	16,169
Loans:
Individually evaluated	153	0	153	0
Collectively evaluated	1,214,903	1,091,296	1,214,903	1,091,296
Loans, net of unearned income	1,215,056	1,091,296	1,215,056	1,091,296
Nonaccruing loans with no allowance for credit losses	153	0	153	0
Real estate – 1-4 family mortgage:
Allowance for loan losses:
Beginning balance	41,910	31,303	32,356	32,165
Charge-offs	(208)	(276)	(532)	(529)
Recoveries	378	193	725	855
Net (charge-offs) recoveries	170	(83)	193	326
Provision for (recovery of provision for) credit losses on loans	1,452	961	10,983	(310)
Ending balance	43,532	32,181	43,532	32,181
Individually evaluated	0	206	0	206
Collectively evaluated	43,532	31,975	43,532	31,975
Loans:
Individually evaluated	5,965	5,311	5,965	5,311
Collectively evaluated	3,121,924	2,719,432	3,121,924	2,719,432
Loans, net of unearned income	3,127,889	2,724,743	3,127,889	2,724,743
Nonaccruing loans with no allowance for credit losses	5,809	3,039	5,809	3,039
Real estate – commercial mortgage:
Allowance for loan losses:
Beginning balance	64,373	74,893	68,940	76,127
Charge-offs	(1,956)	(184)	(2,670)	(416)
Recoveries	50	190	397	504
Net (charge-offs) recoveries	(1,906)	6	(2,273)	88
Provision for (recovery of provision for) credit losses on loans	6,800	(1,004)	2,600	(2,320)
Ending balance	69,267	73,895	69,267	73,895
Individually evaluated	2,649	5,968	2,649	5,968
Collectively evaluated	66,618	67,927	66,618	67,927
Loans:
Individually evaluated	19,043	19,120	19,043	19,120
Collectively evaluated	4,997,622	4,516,610	4,997,622	4,516,610
Loans, net of unearned income	5,016,665	4,535,730	5,016,665	4,535,730
Nonaccruing loans with no allowance for credit losses	4,633	2,865	4,633	2,865
Lease financing
Allowance for loan losses:
Beginning balance	1,802	1,511	1,486	1,624
Charge-offs	0	(13)	(7)	(13)
Recoveries	113	11	136	36
Net (charge-offs) recoveries	113	(2)	129	23
Provision for (recovery of provision for) credit losses on loans	399	61	699	(77)
Ending balance	2,314	1,570	2,314	1,570
Individually evaluated	0	0	0	0
Collectively evaluated	2,314	1,570	2,314	1,570
Loans:
Individually evaluated	0	0	0	0
Collectively evaluated	103,357	79,215	103,357	79,215
Loans, net of unearned income	103,357	79,215	103,357	79,215
Nonaccruing loans with no allowance for credit losses	0	0	0	0
Installment Loans to Individuals
Allowance for loan losses:
Beginning balance	10,563	11,924	11,048	11,150
Charge-offs	(722)	(1,281)	(2,351)	(4,286)
Recoveries	728	1,051	2,271	3,949
Net (charge-offs) recoveries	6	(230)	(80)	(337)
Provision for (recovery of provision for) credit losses on loans	(573)	(448)	(972)	433
Ending balance	9,996	11,246	9,996	11,246
Individually evaluated	370	607	370	607
Collectively evaluated	9,626	10,639	9,626	10,639
Loans:
Individually evaluated	370	617	370	617
Collectively evaluated	128,576	149,204	128,576	149,204
Loans, net of unearned income	128,946	149,821	128,946	149,821
Nonaccruing loans with no allowance for credit losses	$ 2	$ 10	2	$ 10
Cumulative Effect, Period Of Adoption, Adjustment
Allowance for loan losses:
Beginning balance			1,648
Cumulative Effect, Period Of Adoption, Adjustment | Commercial, financial, agricultural
Allowance for loan losses:
Beginning balance			1,648
Cumulative Effect, Period Of Adoption, Adjustment | Real estate – construction:
Allowance for loan losses:
Beginning balance			0
Cumulative Effect, Period Of Adoption, Adjustment | Real estate – 1-4 family mortgage:
Allowance for loan losses:
Beginning balance			0
Cumulative Effect, Period Of Adoption, Adjustment | Real estate – commercial mortgage:
Allowance for loan losses:
Beginning balance			0
Cumulative Effect, Period Of Adoption, Adjustment | Lease financing
Allowance for loan losses:
Beginning balance			0
Cumulative Effect, Period Of Adoption, Adjustment | Installment Loans to Individuals
Allowance for loan losses:
Beginning balance			$ 0