Loans and Allowance for Credit Losses Past Due Loan Status and Non-Accrual Loans by Portfolio Segment (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015	Mar. 31, 2015
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	$ 200,105	$ 196,741
>90 Days Past Due and Accruing	15,013	15,291
Non-accrual	122,170	129,523
Current	13,670,596	13,641,861
Loans, net of unearned income	13,870,701	13,838,602	$ 13,115,505
Real-estate commercial mortage [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	51,560	48,951
>90 Days Past Due and Accruing	2,271	439
Non-accrual	40,861	40,731
Current	5,506,548	5,413,379
Loans, net of unearned income	5,558,108	5,462,330	5,227,101
Commercial - Secured [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	57,631	51,620
>90 Days Past Due and Accruing	2,024	1,853
Non-accrual	36,360	41,498
Current	3,824,066	3,874,493
Loans, net of unearned income	3,881,697	3,926,113
Commercial - unsecured [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	1,171	1,313
>90 Days Past Due and Accruing	0	19
Non-accrual	756	701
Current	152,465	161,536
Loans, net of unearned income	153,636	162,849
Commercial - industrial, financial, and agricultural [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	58,802	52,933
>90 Days Past Due and Accruing	2,024	1,872
Non-accrual	37,116	42,199
Current	3,976,531	4,036,029
Loans, net of unearned income	4,035,333	4,088,962	3,762,631
Real-estate - home equity [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	23,441	23,666
>90 Days Past Due and Accruing	2,914	3,473
Non-accrual	11,494	11,210
Current	1,636,040	1,660,773
Loans, net of unearned income	1,659,481	1,684,439	1,701,623
Real-estate - residential mortgage [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	42,715	46,789
>90 Days Past Due and Accruing	4,402	6,570
Non-accrual	20,780	21,914
Current	1,334,744	1,329,371
Loans, net of unearned income	1,377,459	1,376,160	1,364,788
Construction - Commercial Residential [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	14,306	13,073
>90 Days Past Due and Accruing	1,495	0
Non-accrual	9,294	11,213
Current	167,973	166,230
Loans, net of unearned income	182,279	179,303
Construction - Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	606	864
>90 Days Past Due and Accruing	12	0
Non-accrual	594	638
Current	566,210	559,127
Loans, net of unearned income	566,816	559,991
Construction other [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	1,296	697
>90 Days Past Due and Accruing	0	416
Non-accrual	610	193
Current	60,481	59,997
Loans, net of unearned income	61,777	60,694
Real-estate - construction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	16,208	14,634
>90 Days Past Due and Accruing	1,507	416
Non-accrual	10,498	12,044
Current	794,664	785,354
Loans, net of unearned income	810,872	799,988	677,806
Consumer - direct [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	3,259	4,457
>90 Days Past Due and Accruing	1,597	2,203
Non-accrual	0	0
Current	90,204	94,262
Loans, net of unearned income	93,463	98,719
Consumer - Indirect [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	1,895	3,046
>90 Days Past Due and Accruing	205	237
Non-accrual	0	0
Current	167,863	166,823
Loans, net of unearned income	169,758	169,869
Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	5,154	7,503
>90 Days Past Due and Accruing	1,802	2,440
Non-accrual	0	0
Current	258,067	261,085
Loans, net of unearned income	263,221	268,588	257,301
Leasing and other and overdrafts [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	2,225	2,265
>90 Days Past Due and Accruing	93	81
Non-accrual	1,421	1,425
Current	164,002	155,870
Loans, net of unearned income	166,227	158,135	$ 124,255
Financing Receivables, 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	47,634	40,194
Financing Receivables, 30 to 59 Days Past Due [Member] | Real-estate commercial mortage [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	6,604	6,469
Financing Receivables, 30 to 59 Days Past Due [Member] | Commercial - Secured [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	16,053	5,654
Financing Receivables, 30 to 59 Days Past Due [Member] | Commercial - unsecured [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	415	510
Financing Receivables, 30 to 59 Days Past Due [Member] | Commercial - industrial, financial, and agricultural [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	16,468	6,164
Financing Receivables, 30 to 59 Days Past Due [Member] | Real-estate - home equity [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	7,024	6,438
Financing Receivables, 30 to 59 Days Past Due [Member] | Real-estate - residential mortgage [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	12,136	15,141
Financing Receivables, 30 to 59 Days Past Due [Member] | Construction - Commercial Residential [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	1,550	1,366
Financing Receivables, 30 to 59 Days Past Due [Member] | Construction - Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	50
Financing Receivables, 30 to 59 Days Past Due [Member] | Construction other [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	686	88
Financing Receivables, 30 to 59 Days Past Due [Member] | Real-estate - construction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	2,236	1,504
Financing Receivables, 30 to 59 Days Past Due [Member] | Consumer - direct [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	1,068	1,687
Financing Receivables, 30 to 59 Days Past Due [Member] | Consumer - Indirect [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	1,483	2,308
Financing Receivables, 30 to 59 Days Past Due [Member] | Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	2,551	3,995
Financing Receivables, 30 to 59 Days Past Due [Member] | Leasing and other and overdrafts [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	615	483
Financing Receivables, 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	15,288	11,733
Financing Receivables, 60 to 89 Days Past Due [Member] | Real-estate commercial mortage [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	1,824	1,312
Financing Receivables, 60 to 89 Days Past Due [Member] | Commercial - Secured [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	3,194	2,615
Financing Receivables, 60 to 89 Days Past Due [Member] | Commercial - unsecured [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	83
Financing Receivables, 60 to 89 Days Past Due [Member] | Commercial - industrial, financial, and agricultural [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	3,194	2,698
Financing Receivables, 60 to 89 Days Past Due [Member] | Real-estate - home equity [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	2,009	2,545
Financing Receivables, 60 to 89 Days Past Due [Member] | Real-estate - residential mortgage [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	5,397	3,164
Financing Receivables, 60 to 89 Days Past Due [Member] | Construction - Commercial Residential [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	1,967	494
Financing Receivables, 60 to 89 Days Past Due [Member] | Construction - Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	176
Financing Receivables, 60 to 89 Days Past Due [Member] | Construction other [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	0
Financing Receivables, 60 to 89 Days Past Due [Member] | Real-estate - construction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	1,967	670
Financing Receivables, 60 to 89 Days Past Due [Member] | Consumer - direct [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	594	567
Financing Receivables, 60 to 89 Days Past Due [Member] | Consumer - Indirect [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	207	501
Financing Receivables, 60 to 89 Days Past Due [Member] | Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	801	1,068
Financing Receivables, 60 to 89 Days Past Due [Member] | Leasing and other and overdrafts [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	96	276
Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	137,183	144,814
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Real-estate commercial mortage [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	43,132	41,170
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Commercial - Secured [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	38,384	43,351
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Commercial - unsecured [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	756	720
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Commercial - industrial, financial, and agricultural [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	39,140	44,071
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Real-estate - home equity [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	14,408	14,683
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Real-estate - residential mortgage [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	25,182	28,484
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Construction - Commercial Residential [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	10,789	11,213
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Construction - Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	606	638
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Construction other [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	610	609
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Real-estate - construction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	12,005	12,460
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Consumer - direct [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	1,597	2,203
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Consumer - Indirect [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	205	237
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	1,802	2,440
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Leasing and other and overdrafts [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	$ 1,514	$ 1,506