Loans and Allowance for Credit Losses Past Due Loan Status and Non-Accrual Loans by Portfolio Segment (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
>90 Days Past Due and Accruing	$ 11,106	$ 10,010
Non-accrual	128,572	124,749
Current	15,957,429	15,571,979
Loans, net of unearned income	16,165,800	15,768,247
Commercial – industrial, financial and agricultural
>90 Days Past Due and Accruing	1,119	1,405
Non-accrual	50,150	52,904
Current	4,345,516	4,235,641
Loans, net of unearned income	4,404,548	4,300,297
Real estate – commercial mortgage
>90 Days Past Due and Accruing	1,765	625
Non-accrual	30,388	34,822
Current	6,388,426	6,315,678
Loans, net of unearned income	6,434,285	6,364,804
Commercial - secured
>90 Days Past Due and Accruing	1,068	1,360
Non-accrual	49,299	52,255
Current	4,168,448	4,068,793
Loans, net of unearned income	4,224,980	4,132,440
Commercial - unsecured
>90 Days Past Due and Accruing	51	45
Non-accrual	851	649
Current	177,068	166,848
Loans, net of unearned income	179,568	167,857
Real estate – home equity
>90 Days Past Due and Accruing	3,061	2,372
Non-accrual	6,708	9,135
Current	1,431,666	1,535,557
Loans, net of unearned income	1,452,137	1,559,719
Real estate – residential mortgage
>90 Days Past Due and Accruing	4,433	5,280
Non-accrual	14,668	15,691
Current	2,202,955	1,914,888
Loans, net of unearned income	2,251,044	1,954,711
Real estate – construction
>90 Days Past Due and Accruing	0	0
Non-accrual	7,390	12,197
Current	906,720	993,613
Loans, net of unearned income	916,599	1,006,935
Construction - commercial residential
>90 Days Past Due and Accruing	0	0
Non-accrual	6,881	11,767
Current	108,502	150,896
Loans, net of unearned income	117,872	163,102
Construction - commercial
>90 Days Past Due and Accruing	0	0
Non-accrual	19	19
Current	726,707	765,314
Loans, net of unearned income	726,726	765,816
Construction - other
>90 Days Past Due and Accruing	0	0
Non-accrual	490	411
Current	71,511	77,403
Loans, net of unearned income	72,001	78,017
Consumer
>90 Days Past Due and Accruing	409	296
Non-accrual	0	0
Current	415,034	309,491
Loans, net of unearned income	419,186	313,783
Consumer - direct
>90 Days Past Due and Accruing	66	70
Non-accrual	0	0
Current	55,629	54,828
Loans, net of unearned income	56,033	55,213
Consumer - indirect
>90 Days Past Due and Accruing	343	226
Non-accrual	0	0
Current	359,405	254,663
Loans, net of unearned income	363,153	258,570
Leasing and other and overdrafts
>90 Days Past Due and Accruing	319	32
Non-accrual	19,268	0
Current	267,112	267,111
Loans, net of unearned income	288,001	267,998
30-59 Days Past Due
Total Past Due	53,640	40,709
30-59 Days Past Due | Commercial – industrial, financial and agricultural
Total Past Due	6,825	5,083
30-59 Days Past Due | Real estate – commercial mortgage
Total Past Due	12,206	9,456
30-59 Days Past Due | Commercial - secured
Total Past Due	5,227	4,778
30-59 Days Past Due | Commercial - unsecured
Total Past Due	1,598	305
30-59 Days Past Due | Real estate – home equity
Total Past Due	7,144	9,640
30-59 Days Past Due | Real estate – residential mortgage
Total Past Due	20,796	11,961
30-59 Days Past Due | Real estate – construction
Total Past Due	2,489	686
30-59 Days Past Due | Construction - commercial residential
Total Past Due	2,489	0
30-59 Days Past Due | Construction - commercial
Total Past Due	0	483
30-59 Days Past Due | Construction - other
Total Past Due	0	203
30-59 Days Past Due | Consumer
Total Past Due	3,175	3,315
30-59 Days Past Due | Consumer - direct
Total Past Due	267	260
30-59 Days Past Due | Consumer - indirect
Total Past Due	2,908	3,055
30-59 Days Past Due | Leasing and other and overdrafts
Total Past Due	1,005	568
60-89 Days Past Due
Total Past Due	15,053	20,800
60-89 Days Past Due | Commercial – industrial, financial and agricultural
Total Past Due	938	5,264
60-89 Days Past Due | Real estate – commercial mortgage
Total Past Due	1,500	4,223
60-89 Days Past Due | Commercial - secured
Total Past Due	938	5,254
60-89 Days Past Due | Commercial - unsecured
Total Past Due	0	10
60-89 Days Past Due | Real estate – home equity
Total Past Due	3,558	3,015
60-89 Days Past Due | Real estate – residential mortgage
Total Past Due	8,192	6,891
60-89 Days Past Due | Real estate – construction
Total Past Due	0	439
60-89 Days Past Due | Construction - commercial residential
Total Past Due	0	439
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	568	681
60-89 Days Past Due | Consumer - direct
Total Past Due	71	55
60-89 Days Past Due | Consumer - indirect
Total Past Due	497	626
60-89 Days Past Due | Leasing and other and overdrafts
Total Past Due	$ 297	$ 287