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Allowance for Credit Losses (Aging By Loan Class) (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Financing receivable recorded investment
Past due 90 days or Greater and Still Accruing	$ 8,259	$ 59,705
Past due	39,166	84,450
Loans, current	7,550,069	6,810,496
Total loans	7,589,235	6,894,946
30 to 59 Days
Financing receivable recorded investment
Past due	10,818	18,169
60 to 89 Days
Financing receivable recorded investment
Past due	19,154	4,937
90 Days or Greater
Financing receivable recorded investment
Past due	9,194	61,344
Commercial, financial and agricultural
Financing receivable recorded investment
Total loans	4,426,866	3,379,837
Commercial, financial and agricultural | Domestic | Commercial
Financing receivable recorded investment
Past due 90 days or Greater and Still Accruing	971	421
Past due	4,756	5,052
Loans, current	1,873,223	1,287,608
Total loans	1,877,979	1,292,660
Commercial, financial and agricultural | Domestic | Commercial | 30 to 59 Days
Financing receivable recorded investment
Past due	3,079	3,134
Commercial, financial and agricultural | Domestic | Commercial | 60 to 89 Days
Financing receivable recorded investment
Past due	238	626
Commercial, financial and agricultural | Domestic | Commercial | 90 Days or Greater
Financing receivable recorded investment
Past due	1,439	1,292
Commercial, financial and agricultural | Domestic | Commercial Real Estate: farmland and commercial
Financing receivable recorded investment
Past due 90 days or Greater and Still Accruing		54,878
Past due	1,961	65,017
Loans, current	2,108,989	1,831,730
Total loans	2,110,950	1,896,747
Commercial, financial and agricultural | Domestic | Commercial Real Estate: farmland and commercial | 30 to 59 Days
Financing receivable recorded investment
Past due	1,702	8,058
Commercial, financial and agricultural | Domestic | Commercial Real Estate: farmland and commercial | 60 to 89 Days
Financing receivable recorded investment
Past due	259	2,031
Commercial, financial and agricultural | Domestic | Commercial Real Estate: farmland and commercial | 90 Days or Greater
Financing receivable recorded investment
Past due		54,928
Commercial, financial and agricultural | Domestic | Commercial Real Estate: multifamily
Financing receivable recorded investment
Past due	159	478
Loans, current	437,778	189,952
Total loans	437,937	190,430
Commercial, financial and agricultural | Domestic | Commercial Real Estate: multifamily | 30 to 59 Days
Financing receivable recorded investment
Past due	22	313
Commercial, financial and agricultural | Domestic | Commercial Real Estate: multifamily | 60 to 89 Days
Financing receivable recorded investment
Past due	137
Commercial, financial and agricultural | Domestic | Commercial Real Estate: multifamily | 90 Days or Greater
Financing receivable recorded investment
Past due		165
Real estate - construction
Financing receivable recorded investment
Total loans	1,943,430	2,185,883
Real estate - construction | Domestic | Commercial Real Estate: other construction and land development
Financing receivable recorded investment
Past due 90 days or Greater and Still Accruing	142
Past due	18,987	564
Loans, current	1,924,443	2,185,319
Total loans	1,943,430	2,185,883
Real estate - construction | Domestic | Commercial Real Estate: other construction and land development | 30 to 59 Days
Financing receivable recorded investment
Past due	2,242	509
Real estate - construction | Domestic | Commercial Real Estate: other construction and land development | 60 to 89 Days
Financing receivable recorded investment
Past due	16,603	55
Real estate - construction | Domestic | Commercial Real Estate: other construction and land development | 90 Days or Greater
Financing receivable recorded investment
Past due	142
Real estate - mortgage
Financing receivable recorded investment
Total loans	1,033,646	1,140,377
Real estate - mortgage | Domestic | Residential First Lien
Financing receivable recorded investment
Past due 90 days or Greater and Still Accruing	5,963	3,107
Past due	9,625	8,559
Loans, current	400,390	425,342
Total loans	410,015	433,901
Real estate - mortgage | Domestic | Residential First Lien | 30 to 59 Days
Financing receivable recorded investment
Past due	2,288	3,229
Real estate - mortgage | Domestic | Residential First Lien | 60 to 89 Days
Financing receivable recorded investment
Past due	910	1,670
Real estate - mortgage | Domestic | Residential First Lien | 90 Days or Greater
Financing receivable recorded investment
Past due	6,427	3,660
Real estate - mortgage | Domestic | Residential Junior Lien
Financing receivable recorded investment
Past due 90 days or Greater and Still Accruing	945	1,200
Past due	2,231	2,789
Loans, current	621,400	703,687
Total loans	623,631	706,476
Real estate - mortgage | Domestic | Residential Junior Lien | 30 to 59 Days
Financing receivable recorded investment
Past due	564	1,112
Real estate - mortgage | Domestic | Residential Junior Lien | 60 to 89 Days
Financing receivable recorded investment
Past due	722	477
Real estate - mortgage | Domestic | Residential Junior Lien | 90 Days or Greater
Financing receivable recorded investment
Past due	945	1,200
Consumer
Financing receivable recorded investment
Total loans	41,110	47,800
Consumer | Domestic
Financing receivable recorded investment
Past due 90 days or Greater and Still Accruing	33	88
Past due	531	630
Loans, current	40,579	47,170
Total loans	41,110	47,800
Consumer | Domestic | 30 to 59 Days
Financing receivable recorded investment
Past due	460	467
Consumer | Domestic | 60 to 89 Days
Financing receivable recorded investment
Past due	35	75
Consumer | Domestic | 90 Days or Greater
Financing receivable recorded investment
Past due	36	88
Foreign
Financing receivable recorded investment
Total loans	144,183	141,049
Foreign | Foreign
Financing receivable recorded investment
Past due 90 days or Greater and Still Accruing	205	11
Past due	916	1,361
Loans, current	143,267	139,688
Total loans	144,183	141,049
Foreign | Foreign | 30 to 59 Days
Financing receivable recorded investment
Past due	461	1,347
Foreign | Foreign | 60 to 89 Days
Financing receivable recorded investment
Past due	250	3
Foreign | Foreign | 90 Days or Greater
Financing receivable recorded investment
Past due	$ 205	$ 11

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