Loans and Allowance for Credit Losses Past Due Loan Status and Non-Accrual Loans by Portfolio Segment (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016	Sep. 30, 2016
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	$ 198,716	$ 186,787
≥ 90 Days Past Due and Accruing	13,124	11,505
Non- accrual	123,345	120,133
Current	15,288,183	14,512,485
Loans, net of unearned income	15,486,899	14,699,272	$ 14,391,238
Financing Receivables, 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	49,493	41,938
Financing Receivables, 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	12,754	13,211
Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	136,469	131,638
Real-estate - commercial mortgage
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	47,223	47,195
≥ 90 Days Past Due and Accruing	2,884	383
Non- accrual	31,766	38,936
Current	6,227,917	5,971,387
Loans, net of unearned income	6,275,140	6,018,582	5,818,915
Real-estate - commercial mortgage | Financing Receivables, 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	10,276	6,254
Real-estate - commercial mortgage | Financing Receivables, 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	2,297	1,622
Real-estate - commercial mortgage | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	34,650	39,319
Commercial - secured
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	64,050	51,824
≥ 90 Days Past Due and Accruing	1,503	959
Non- accrual	51,787	41,589
Current	4,024,908	3,881,728
Loans, net of unearned income	4,088,958	3,933,552
Commercial - secured | Financing Receivables, 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	8,382	6,660
Commercial - secured | Financing Receivables, 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	2,378	2,616
Commercial - secured | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	53,290	42,548
Commercial - unsecured
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	1,067	1,845
≥ 90 Days Past Due and Accruing	0	152
Non- accrual	919	760
Current	133,050	152,089
Loans, net of unearned income	134,117	153,934
Commercial - unsecured | Financing Receivables, 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	114	898
Commercial - unsecured | Financing Receivables, 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	34	35
Commercial - unsecured | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	919	912
Commercial - industrial, financial and agricultural
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	65,117	53,669
≥ 90 Days Past Due and Accruing	1,503	1,111
Non- accrual	52,706	42,349
Current	4,157,958	4,033,817
Loans, net of unearned income	4,223,075	4,087,486	4,024,119
Commercial - industrial, financial and agricultural | Financing Receivables, 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	8,496	7,558
Commercial - industrial, financial and agricultural | Financing Receivables, 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	2,412	2,651
Commercial - industrial, financial and agricultural | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	54,209	43,460
Real-estate - home equity
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	25,184	22,428
≥ 90 Days Past Due and Accruing	3,096	2,543
Non- accrual	9,133	10,611
Current	1,542,289	1,602,687
Loans, net of unearned income	1,567,473	1,625,115	1,640,421
Real-estate - home equity | Financing Receivables, 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	11,192	6,596
Real-estate - home equity | Financing Receivables, 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	1,763	2,678
Real-estate - home equity | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	12,229	13,154
Real estate - residential mortgage
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	42,412	43,999
≥ 90 Days Past Due and Accruing	5,258	5,224
Non- accrual	16,385	18,431
Current	1,845,495	1,557,995
Loans, net of unearned income	1,887,907	1,601,994	1,542,696
Real estate - residential mortgage | Financing Receivables, 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	15,106	15,600
Real estate - residential mortgage | Financing Receivables, 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	5,663	4,744
Real estate - residential mortgage | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	21,643	23,655
Construction - commercial residential
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	12,642	8,595
≥ 90 Days Past Due and Accruing	60	36
Non- accrual	12,164	8,275
Current	143,485	133,594
Loans, net of unearned income	156,127	142,189
Construction - commercial residential | Financing Receivables, 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	400	233
Construction - commercial residential | Financing Receivables, 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	18	51
Construction - commercial residential | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	12,224	8,311
Construction - commercial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	466	1,178
≥ 90 Days Past Due and Accruing	0	0
Non- accrual	100	435
Current	750,932	643,312
Loans, net of unearned income	751,398	644,490
Construction - commercial | Financing Receivables, 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	366	743
Construction - commercial | Financing Receivables, 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	0
Construction - commercial | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	100	435
Construction - other
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	1,473	1,096
≥ 90 Days Past Due and Accruing	0	0
Non- accrual	1,091	1,096
Current	64,110	55,874
Loans, net of unearned income	65,583	56,970
Construction - other | Financing Receivables, 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	382	0
Construction - other | Financing Receivables, 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	0
Construction - other | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	1,091	1,096
Real-estate - construction
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	14,581	10,869
≥ 90 Days Past Due and Accruing	60	36
Non- accrual	13,355	9,806
Current	958,527	832,780
Loans, net of unearned income	973,108	843,649	861,634
Real-estate - construction | Financing Receivables, 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	1,148	976
Real-estate - construction | Financing Receivables, 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	18	51
Real-estate - construction | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	13,415	9,842
Consumer - direct
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	221	3,315
≥ 90 Days Past Due and Accruing	63	1,563
Non- accrual	0	0
Current	55,490	93,572
Loans, net of unearned income	55,711	96,887
Consumer - direct | Financing Receivables, 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	118	1,211
Consumer - direct | Financing Receivables, 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	40	541
Consumer - direct | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	63	1,563
Consumer - indirect
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	3,014	3,927
≥ 90 Days Past Due and Accruing	180	328
Non- accrual	0	0
Current	243,723	190,656
Loans, net of unearned income	246,737	194,583
Consumer - indirect | Financing Receivables, 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	2,393	3,200
Consumer - indirect | Financing Receivables, 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	441	399
Consumer - indirect | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	180	328
Consumer
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	3,235	7,242
≥ 90 Days Past Due and Accruing	243	1,891
Non- accrual	0	0
Current	299,213	284,228
Loans, net of unearned income	302,448	291,470	283,673
Consumer | Financing Receivables, 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	2,511	4,411
Consumer | Financing Receivables, 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	481	940
Consumer | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	243	1,891
Leasing, other and overdrafts
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	964	1,385
≥ 90 Days Past Due and Accruing	80	317
Non- accrual	0	0
Current	256,784	229,591
Loans, net of unearned income	257,748	230,976	$ 219,780
Leasing, other and overdrafts | Financing Receivables, 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	764	543
Leasing, other and overdrafts | Financing Receivables, 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	120	525
Leasing, other and overdrafts | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	$ 80	$ 317