Allowance for Credit Losses (Portfolio Credit Quality) (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Loan portfolio by credit quality indicator
2020	$ 2,090,901
2019	2,347,379
2018	1,435,691
2017	764,038
2016	385,473
Prior	478,325
Total loans	7,501,807	$ 6,894,946
Pass
Loan portfolio by credit quality indicator
Total loans		6,538,085
Special Review
Loan portfolio by credit quality indicator
Total loans		33,553
Watch List - Pass
Loan portfolio by credit quality indicator
Total loans		62,315
Watch List - Substandard
Loan portfolio by credit quality indicator
Total loans		248,318
Commercial, financial and agricultural
Loan portfolio by credit quality indicator
Total loans	3,967,980	3,379,837
Commercial, financial and agricultural | Domestic | Commercial
Loan portfolio by credit quality indicator
2020	982,334
2019	407,874
2018	242,980
2017	140,339
2016	21,294
Prior	12,670
Total loans	1,807,491	1,292,660
Commercial, financial and agricultural | Domestic | Commercial | Pass
Loan portfolio by credit quality indicator
2020	909,494
2019	373,023
2018	212,414
2017	140,118
2016	20,898
Prior	12,645
Total loans	1,668,592	1,228,110
Commercial, financial and agricultural | Domestic | Commercial | Special Review
Loan portfolio by credit quality indicator
2020	71,497
2019	569
Total loans	72,066	569
Commercial, financial and agricultural | Domestic | Commercial | Watch List - Pass
Loan portfolio by credit quality indicator
2020	530
2019	33,949
2018	29,644
Prior	25
Total loans	64,148	39
Commercial, financial and agricultural | Domestic | Commercial | Watch List - Substandard
Loan portfolio by credit quality indicator
2019	3
2018	708
2016	378
Total loans	1,089	62,007
Commercial, financial and agricultural | Domestic | Commercial | Watch List - Doubtful
Loan portfolio by credit quality indicator
2020	813
2019	330
2018	214
2017	221
2016	18
Total loans	1,596
Commercial, financial and agricultural | Domestic | Commercial Real Estate: farmland and commercial
Loan portfolio by credit quality indicator
2020	400,136
2019	622,078
2018	366,336
2017	195,999
2016	212,934
Prior	174,151
Total loans	1,971,634	1,896,747
Commercial, financial and agricultural | Domestic | Commercial Real Estate: farmland and commercial | Pass
Loan portfolio by credit quality indicator
2020	373,126
2019	558,263
2018	339,142
2017	184,595
2016	201,642
Prior	169,981
Total loans	1,826,749	1,710,446
Commercial, financial and agricultural | Domestic | Commercial Real Estate: farmland and commercial | Special Review
Loan portfolio by credit quality indicator
2020	938
2018	4,702
2017	175
2016	3,207
Prior	420
Total loans	9,442	13,184
Commercial, financial and agricultural | Domestic | Commercial Real Estate: farmland and commercial | Watch List - Pass
Loan portfolio by credit quality indicator
2020	22,701
2019	7,933
2018	22,300
2017	8,878
2016	7,448
Total loans	69,260	20,183
Commercial, financial and agricultural | Domestic | Commercial Real Estate: farmland and commercial | Watch List - Substandard
Loan portfolio by credit quality indicator
2020	3,371
2019	55,639
2018	192
2017	2,312
2016	637
Prior	3,496
Total loans	65,647	151,726
Commercial, financial and agricultural | Domestic | Commercial Real Estate: farmland and commercial | Watch List - Doubtful
Loan portfolio by credit quality indicator
2019	243
2017	39
Prior	254
Total loans	536
Commercial, financial and agricultural | Domestic | Commercial Real Estate: multifamily
Loan portfolio by credit quality indicator
2020	25,101
2019	59,134
2018	17,867
2017	64,576
2016	9,704
Prior	12,473
Total loans	188,855	190,430
Commercial, financial and agricultural | Domestic | Commercial Real Estate: multifamily | Pass
Loan portfolio by credit quality indicator
2020	24,964
2019	59,134
2018	17,867
2017	64,576
2016	9,704
Prior	12,473
Total loans	188,718	190,265
Commercial, financial and agricultural | Domestic | Commercial Real Estate: multifamily | Watch List - Doubtful
Loan portfolio by credit quality indicator
2020	137
Total loans	137
Real estate - construction
Loan portfolio by credit quality indicator
Total loans	2,277,991	2,185,883
Real estate - construction | Domestic | Commercial Real Estate: other construction and land development
Loan portfolio by credit quality indicator
2020	460,019
2019	980,340
2018	622,563
2017	186,950
2016	14,952
Prior	13,167
Total loans	2,277,991	2,185,883
Real estate - construction | Domestic | Commercial Real Estate: other construction and land development | Pass
Loan portfolio by credit quality indicator
2020	426,830
2019	951,765
2018	622,403
2017	186,950
2016	14,952
Prior	13,165
Total loans	2,216,065	2,090,370
Real estate - construction | Domestic | Commercial Real Estate: other construction and land development | Special Review
Loan portfolio by credit quality indicator
2020	16,106
Total loans	16,106	18,721
Real estate - construction | Domestic | Commercial Real Estate: other construction and land development | Watch List - Pass
Loan portfolio by credit quality indicator
2020	16,587
2019	27,782
2018	160
Prior	1
Total loans	44,530	41,949
Real estate - construction | Domestic | Commercial Real Estate: other construction and land development | Watch List - Substandard
Loan portfolio by credit quality indicator
2020	376
Total loans	376	33,905
Real estate - construction | Domestic | Commercial Real Estate: other construction and land development | Watch List - Doubtful
Loan portfolio by credit quality indicator
2020	120
2019	793
Prior	1
Total loans	914
Real estate - mortgage
Loan portfolio by credit quality indicator
Total loans	1,081,380	1,140,377
Real estate - mortgage | Domestic | Residential First Lien
Loan portfolio by credit quality indicator
2020	41,957
2019	71,159
2018	83,698
2017	61,827
2016	39,404
Prior	123,493
Total loans	421,538	433,901
Real estate - mortgage | Domestic | Residential First Lien | Pass
Loan portfolio by credit quality indicator
2020	41,868
2019	71,145
2018	83,502
2017	61,827
2016	39,018
Prior	123,421
Total loans	420,781	426,546
Real estate - mortgage | Domestic | Residential First Lien | Special Review
Loan portfolio by credit quality indicator
2016	245
Total loans	245	253
Real estate - mortgage | Domestic | Residential First Lien | Watch List - Pass
Loan portfolio by credit quality indicator
2019	14
2018	129
Total loans	143	144
Real estate - mortgage | Domestic | Residential First Lien | Watch List - Substandard
Loan portfolio by credit quality indicator
2018	67
2016	50
Total loans	117	680
Real estate - mortgage | Domestic | Residential First Lien | Watch List - Doubtful
Loan portfolio by credit quality indicator
2020	89
2016	91
Prior	72
Total loans	252
Real estate - mortgage | Domestic | Residential Junior Lien
Loan portfolio by credit quality indicator
2020	111,607
2019	139,225
2018	85,315
2017	106,971
2016	82,878
Prior	133,846
Total loans	659,842	706,476
Real estate - mortgage | Domestic | Residential Junior Lien | Pass
Loan portfolio by credit quality indicator
2020	111,607
2019	139,225
2018	85,274
2017	106,161
2016	82,878
Prior	133,846
Total loans	658,991	704,958
Real estate - mortgage | Domestic | Residential Junior Lien | Special Review
Loan portfolio by credit quality indicator
2017	810
Total loans	810	826
Real estate - mortgage | Domestic | Residential Junior Lien | Watch List - Doubtful
Loan portfolio by credit quality indicator
2018	41
Total loans	41
Consumer
Loan portfolio by credit quality indicator
Total loans	42,401	47,800
Consumer | Domestic
Loan portfolio by credit quality indicator
2020	19,513
2019	18,497
2018	2,387
2017	404
2016	152
Prior	1,448
Total loans	42,401	47,800
Consumer | Domestic | Pass
Loan portfolio by credit quality indicator
2020	19,513
2019	18,497
2018	2,387
2017	404
2016	152
Prior	1,445
Total loans	42,398	46,605
Consumer | Domestic | Watch List - Doubtful
Loan portfolio by credit quality indicator
Prior	3
Total loans	3
Foreign
Loan portfolio by credit quality indicator
Total loans	132,055	141,049
Foreign | Foreign
Loan portfolio by credit quality indicator
2020	50,234
2019	49,072
2018	14,545
2017	6,972
2016	4,155
Prior	7,077
Total loans	132,055	141,049
Foreign | Foreign | Pass
Loan portfolio by credit quality indicator
2020	50,234
2019	49,072
2018	14,545
2017	6,972
2016	4,155
Prior	7,077
Total loans	$ 132,055	$ 140,785