Loans and Allowance for Credit Losses Past Due Loan Status and Non-Accrual Loans by Portfolio Segment (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
>90 Days Past Due and Accruing	$ 10,010	$ 11,505
Non-accrual	124,749	120,133
Total Past Due	196,268	186,787
Current	15,571,979	14,512,485
Loans, net of unearned income	15,768,247	14,699,272
Commercial – industrial, financial and agricultural
>90 Days Past Due and Accruing	1,405	1,111
Non-accrual	52,904	42,349
Total Past Due	64,656	53,669
Current	4,235,641	4,033,817
Loans, net of unearned income	4,300,297	4,087,486
Real estate – commercial mortgage
>90 Days Past Due and Accruing	625	383
Non-accrual	34,822	38,936
Total Past Due	49,126	47,195
Current	6,315,678	5,971,387
Loans, net of unearned income	6,364,804	6,018,582
Commercial - secured
>90 Days Past Due and Accruing	1,360	959
Non-accrual	52,255	41,589
Total Past Due	63,647	51,824
Current	4,068,793	3,881,728
Loans, net of unearned income	4,132,440	3,933,552
Commercial - unsecured
>90 Days Past Due and Accruing	45	152
Non-accrual	649	760
Total Past Due	1,009	1,845
Current	166,848	152,089
Loans, net of unearned income	167,857	153,934
Real estate – home equity
>90 Days Past Due and Accruing	2,372	2,543
Non-accrual	9,135	10,611
Total Past Due	24,162	22,428
Current	1,535,557	1,602,687
Loans, net of unearned income	1,559,719	1,625,115
Real estate – residential mortgage
>90 Days Past Due and Accruing	5,280	5,224
Non-accrual	15,691	18,431
Total Past Due	39,823	43,999
Current	1,914,888	1,557,995
Loans, net of unearned income	1,954,711	1,601,994
Real estate – construction
>90 Days Past Due and Accruing	0	36
Non-accrual	12,197	9,806
Total Past Due	13,322	10,869
Current	993,613	832,780
Loans, net of unearned income	1,006,935	843,649
Construction - commercial residential
>90 Days Past Due and Accruing	0	36
Non-accrual	11,767	8,275
Total Past Due	12,206	8,595
Current	150,896	133,594
Loans, net of unearned income	163,102	142,189
Construction - commercial
>90 Days Past Due and Accruing	0	0
Non-accrual	19	435
Total Past Due	502	1,178
Current	765,314	643,312
Loans, net of unearned income	765,816	644,490
Construction - other
>90 Days Past Due and Accruing	0	0
Non-accrual	411	1,096
Total Past Due	614	1,096
Current	77,403	55,874
Loans, net of unearned income	78,017	56,970
Consumer
>90 Days Past Due and Accruing	296	1,891
Non-accrual	0	0
Total Past Due	4,292	7,242
Current	309,491	284,228
Loans, net of unearned income	313,783	291,470
Consumer - direct
>90 Days Past Due and Accruing	70	1,563
Non-accrual	0	0
Total Past Due	385	3,315
Current	54,828	93,572
Loans, net of unearned income	55,213	96,887
Consumer - indirect
>90 Days Past Due and Accruing	226	328
Non-accrual	0	0
Total Past Due	3,907	3,927
Current	254,663	190,656
Loans, net of unearned income	258,570	194,583
Leasing and other and overdrafts
>90 Days Past Due and Accruing	32	317
Non-accrual	0	0
Total Past Due	887	1,385
Current	267,111	229,591
Loans, net of unearned income	267,998	230,976
30-59 Days Past Due
Total Past Due	40,709	41,938
30-59 Days Past Due | Commercial – industrial, financial and agricultural
Total Past Due	5,083	7,558
30-59 Days Past Due | Real estate – commercial mortgage
Total Past Due	9,456	6,254
30-59 Days Past Due | Commercial - secured
Total Past Due	4,778	6,660
30-59 Days Past Due | Commercial - unsecured
Total Past Due	305	898
30-59 Days Past Due | Real estate – home equity
Total Past Due	9,640	6,596
30-59 Days Past Due | Real estate – residential mortgage
Total Past Due	11,961	15,600
30-59 Days Past Due | Real estate – construction
Total Past Due	686	976
30-59 Days Past Due | Construction - commercial residential
Total Past Due	0	233
30-59 Days Past Due | Construction - commercial
Total Past Due	483	743
30-59 Days Past Due | Construction - other
Total Past Due	203	0
30-59 Days Past Due | Consumer
Total Past Due	3,315	4,411
30-59 Days Past Due | Consumer - direct
Total Past Due	260	1,211
30-59 Days Past Due | Consumer - indirect
Total Past Due	3,055	3,200
30-59 Days Past Due | Leasing and other and overdrafts
Total Past Due	568	543
60-89 Days Past Due
Total Past Due	20,800	13,211
60-89 Days Past Due | Commercial – industrial, financial and agricultural
Total Past Due	5,264	2,651
60-89 Days Past Due | Real estate – commercial mortgage
Total Past Due	4,223	1,622
60-89 Days Past Due | Commercial - secured
Total Past Due	5,254	2,616
60-89 Days Past Due | Commercial - unsecured
Total Past Due	10	35
60-89 Days Past Due | Real estate – home equity
Total Past Due	3,015	2,678
60-89 Days Past Due | Real estate – residential mortgage
Total Past Due	6,891	4,744
60-89 Days Past Due | Real estate – construction
Total Past Due	439	51
60-89 Days Past Due | Construction - commercial residential
Total Past Due	439	51
60-89 Days Past Due | Construction - commercial
Total Past Due	0	0
60-89 Days Past Due | Construction - other
Total Past Due	0	0
60-89 Days Past Due | Consumer
Total Past Due	681	940
60-89 Days Past Due | Consumer - direct
Total Past Due	55	541
60-89 Days Past Due | Consumer - indirect
Total Past Due	626	399
60-89 Days Past Due | Leasing and other and overdrafts
Total Past Due	287	525
Total ≥ 90 Days
Total Past Due	134,759	131,638
Total ≥ 90 Days | Commercial – industrial, financial and agricultural
Total Past Due	54,309	43,460
Total ≥ 90 Days | Real estate – commercial mortgage
Total Past Due	35,447	39,319
Total ≥ 90 Days | Commercial - secured
Total Past Due	53,615	42,548
Total ≥ 90 Days | Commercial - unsecured
Total Past Due	694	912
Total ≥ 90 Days | Real estate – home equity
Total Past Due	11,507	13,154
Total ≥ 90 Days | Real estate – residential mortgage
Total Past Due	20,971	23,655
Total ≥ 90 Days | Real estate – construction
Total Past Due	12,197	9,842
Total ≥ 90 Days | Construction - commercial residential
Total Past Due	11,767	8,311
Total ≥ 90 Days | Construction - commercial
Total Past Due	19	435
Total ≥ 90 Days | Construction - other
Total Past Due	411	1,096
Total ≥ 90 Days | Consumer
Total Past Due	296	1,891
Total ≥ 90 Days | Consumer - direct
Total Past Due	70	1,563
Total ≥ 90 Days | Consumer - indirect
Total Past Due	226	328
Total ≥ 90 Days | Leasing and other and overdrafts
Total Past Due	$ 32	$ 317