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Allowance for Credit Losses (Impairment By Loan Class) (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Loan loss allowances, impaired financing receivable, evaluated individually or collectively
Loans Individually Evaluated for Impairment, Recorded Investment	$ 2,681	$ 19,447
Loans Individually Evaluated for Impairment, Allowance	279	279
Loans Collectively Evaluated for Impairment, Recorded Investment	7,459,677	7,522,307
Loans Collectively Evaluated for Impairment, Allowance	108,129	108,780
Commercial, financial and agricultural | Domestic | Commercial Loan [Member]
Loan loss allowances, impaired financing receivable, evaluated individually or collectively
Loans Individually Evaluated for Impairment, Recorded Investment	1,055	1,189
Loans Individually Evaluated for Impairment, Allowance	209	209
Loans Collectively Evaluated for Impairment, Recorded Investment	1,739,552	1,784,747
Loans Collectively Evaluated for Impairment, Allowance	21,954	21,699
Commercial, financial and agricultural | Domestic | Commercial Real Estate Farmland and Commercial Receivable [Member]
Loan loss allowances, impaired financing receivable, evaluated individually or collectively
Loans Individually Evaluated for Impairment, Recorded Investment	422	439
Loans Collectively Evaluated for Impairment, Recorded Investment	2,420,870	2,288,869
Loans Collectively Evaluated for Impairment, Allowance	32,203	30,000
Commercial, financial and agricultural | Domestic | Commercial Real Estate Multifamily Receivable [Member]
Loan loss allowances, impaired financing receivable, evaluated individually or collectively
Loans Individually Evaluated for Impairment, Recorded Investment	127	134
Loans Collectively Evaluated for Impairment, Recorded Investment	518,857	440,910
Loans Collectively Evaluated for Impairment, Allowance	5,935	5,051
Real estate - construction | Domestic | Commercial Real Estate: other construction and land development
Loan loss allowances, impaired financing receivable, evaluated individually or collectively
Loans Individually Evaluated for Impairment, Recorded Investment	892	17,496
Loans Individually Evaluated for Impairment, Allowance	70	70
Loans Collectively Evaluated for Impairment, Recorded Investment	1,652,526	1,829,261
Loans Collectively Evaluated for Impairment, Allowance	34,336	37,542
Real estate - mortgage | Domestic | Residential First Mortgage Financing Receivable [Member]
Loan loss allowances, impaired financing receivable, evaluated individually or collectively
Loans Individually Evaluated for Impairment, Recorded Investment	147	151
Loans Collectively Evaluated for Impairment, Recorded Investment	401,549	404,968
Loans Collectively Evaluated for Impairment, Allowance	3,917	3,874
Real estate - mortgage | Domestic | Residential Junior Lien
Loan loss allowances, impaired financing receivable, evaluated individually or collectively
Loans Individually Evaluated for Impairment, Recorded Investment	38	38
Loans Collectively Evaluated for Impairment, Recorded Investment	549,048	593,987
Loans Collectively Evaluated for Impairment, Allowance	8,736	9,570
Consumer | Domestic
Loan loss allowances, impaired financing receivable, evaluated individually or collectively
Loans Collectively Evaluated for Impairment, Recorded Investment	39,743	40,595
Loans Collectively Evaluated for Impairment, Allowance	279	291
Foreign | Foreign
Loan loss allowances, impaired financing receivable, evaluated individually or collectively
Loans Collectively Evaluated for Impairment, Recorded Investment	137,532	138,970
Loans Collectively Evaluated for Impairment, Allowance	$ 769	$ 753

X

- Definition

The valuation allowance for financing receivables that are expected to be uncollectible that were collectively evaluated for impairment.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (g)
-URI http://asc.fasb.org/extlink&oid=121611835&loc=SL6953423-111524

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- Definition

Amount of valuation allowance for financing receivables that are expected to be uncollectible that were individually evaluated for impairment.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (g)
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+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (h)
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+ References

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-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
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