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Allowance for Credit Losses - By Loan Class (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023	Dec. 31, 2023
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Balance at the beginning of the period	$ 142,798	$ 133,557	$ 157,069	$ 125,972	$ 125,972
Losses charged to allowance	(4,260)	(2,982)	(32,084)	(5,015)
Recoveries credited to allowance	1,300	1,112	1,875	2,143
Net losses charged to allowance	(2,960)	(1,870)	(30,209)	(2,872)
Provision (credit) charged to operations	8,771	8,816	21,749	17,403
Balance at the end of the period	148,609	140,503	148,609	140,503	157,069
Commercial, financial and agricultural | Commercial.
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Charge-down due to customer filing bankruptcy			25,600
Impact on credit loss expense due to customer filing bankruptcy			4,300
Commercial, financial and agricultural | Domestic | Commercial.
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Balance at the beginning of the period	26,676	27,788	35,550	26,728	26,728
Losses charged to allowance	(1,979)	(2,792)	(29,720)	(4,763)	(9,664)
Recoveries credited to allowance	1,234	556	1,789	1,181
Net losses charged to allowance	(745)	(2,236)	(27,931)	(3,582)
Provision (credit) charged to operations	1,324	2,093	19,636	4,499
Balance at the end of the period	27,255	27,645	27,255	27,645	35,550
Commercial, financial and agricultural | Domestic | Commercial real estate: farmland & commercial
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Balance at the beginning of the period	39,402	36,556	42,703	36,474	36,474
Recoveries credited to allowance	6	6	10	11
Net losses charged to allowance	6	6	10	11
Provision (credit) charged to operations	5,480	2,126	2,175	2,203
Balance at the end of the period	44,888	38,688	44,888	38,688	42,703
Commercial, financial and agricultural | Domestic | Commercial real estate: multifamily
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Balance at the beginning of the period	3,768	3,984	5,088	3,794	3,794
Provision (credit) charged to operations	(240)	122	(1,560)	312
Balance at the end of the period	3,528	4,106	3,528	4,106	5,088
Obligations of states and political subdivisions | Domestic | Commercial Real Estate: other construction and land development
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Balance at the beginning of the period	55,097	50,933	55,291	44,684	44,684
Losses charged to allowance	(2,228)		(2,228)
Recoveries credited to allowance		526		837
Net losses charged to allowance	(2,228)	526	(2,228)	837
Provision (credit) charged to operations	1,971	1,605	1,777	7,543
Balance at the end of the period	54,840	53,064	54,840	53,064	55,291
Real estate - mortgage | Domestic | Residential: first lien
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Balance at the beginning of the period	5,757	4,559	5,812	4,759	4,759
Losses charged to allowance	(1)		(46)		(43)
Recoveries credited to allowance	34	1	36	8
Net losses charged to allowance	33	1	(10)	8
Provision (credit) charged to operations	16	532	4	325
Balance at the end of the period	5,806	5,092	5,806	5,092	5,812
Real estate - mortgage | Domestic | Residential Junior Lien
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Balance at the beginning of the period	10,648	8,357	11,024	8,284	8,284
Losses charged to allowance		(164)		(165)	(298)
Recoveries credited to allowance	26	15	35	92
Net losses charged to allowance	26	(149)	35	(73)
Provision (credit) charged to operations	(35)	2,234	(420)	2,231
Balance at the end of the period	10,639	10,442	10,639	10,442	11,024
Consumer | Domestic
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Balance at the beginning of the period	313	291	318	281	281
Losses charged to allowance	(52)	(26)	(90)	(87)	(179)
Recoveries credited to allowance		8	5	14
Net losses charged to allowance	(52)	(18)	(85)	(73)
Provision (credit) charged to operations	53	13	81	78
Balance at the end of the period	314	286	314	286	318
Foreign. | Foreign
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Balance at the beginning of the period	1,137	1,089	1,283	968	968
Provision (credit) charged to operations	202	91	56	212
Balance at the end of the period	$ 1,339	$ 1,180	$ 1,339	$ 1,180	$ 1,283

X

- Definition

Amount, excluding accrued interest, of decrease in allowance for credit loss on financing receivable from writeoff due to bankruptcy of customer.

+ References

No definition available.

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Amount excluding accrued interest, of allowance for credit loss on financing receivable. Excludes net investment in lease.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479344/326-20-45-1

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- Definition

Amount, excluding accrued interest, of increase in allowance for credit loss on financing receivable from recovery. Excludes net investment in lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (e)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-13

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+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-6

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+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-13

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-Publisher FASB
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