Loans and Allowance for Credit Losses Past Due Loan Status and Non-Accrual Loans by Portfolio Segment (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013	Sep. 30, 2013
Financial Receivable, Recorded investment, Past Due [Line Items]
31-59 Days Past Due	$ 58,007	$ 60,774
60-89 Days Past Due	17,969	16,893
>90 Days Past Due and Accruing	17,428	20,524
Non-accrual	126,420	133,753
Total >90 Days	143,848	154,277
Total Past Due	219,824	231,944
Current	12,810,581	12,550,276
Loans, net of unearned income	13,030,405	12,782,220	12,780,899
Real-estate commercial mortage [Member]
Financial Receivable, Recorded investment, Past Due [Line Items]
31-59 Days Past Due	19,506	15,474
60-89 Days Past Due	5,074	4,009
>90 Days Past Due and Accruing	1,755	3,502
Non-accrual	42,847	40,566
Total >90 Days	44,602	44,068
Total Past Due	69,182	63,551
Current	5,087,797	5,038,371
Loans, net of unearned income	5,156,979	5,101,922	5,063,373
Commercial - industrial, financial, and agricultural [Member]
Financial Receivable, Recorded investment, Past Due [Line Items]
31-59 Days Past Due	9,058	9,248
60-89 Days Past Due	1,424	1,490
>90 Days Past Due and Accruing	2,292	1,311
Non-accrual	30,985	36,710
Total >90 Days	33,277	38,021
Total Past Due	43,759	48,759
Current	3,647,503	3,579,661
Loans, net of unearned income	3,691,262	3,628,420	3,645,270
Commercial - Secured [Member]
Financial Receivable, Recorded investment, Past Due [Line Items]
31-59 Days Past Due	7,530	8,916
60-89 Days Past Due	1,215	1,365
>90 Days Past Due and Accruing	2,292	1,311
Non-accrual	30,231	35,774
Total >90 Days	32,523	37,085
Total Past Due	41,268	47,366
Current	3,469,872	3,356,797
Loans, net of unearned income	3,511,140	3,404,163
Commercial - unsecured [Member]
Financial Receivable, Recorded investment, Past Due [Line Items]
31-59 Days Past Due	1,528	332
60-89 Days Past Due	209	125
>90 Days Past Due and Accruing	0	0
Non-accrual	754	936
Total >90 Days	754	936
Total Past Due	2,491	1,393
Current	177,631	222,864
Loans, net of unearned income	180,122	224,257
Real-estate - construction [Member]
Financial Receivable, Recorded investment, Past Due [Line Items]
31-59 Days Past Due	215	14
60-89 Days Past Due	0	645
>90 Days Past Due and Accruing	205	346
Non-accrual	19,655	20,921
Total >90 Days	19,860	21,267
Total Past Due	20,075	21,926
Current	667,653	551,746
Loans, net of unearned income	687,728	573,672	577,342
Real-estate - home equity [Member]
Financial Receivable, Recorded investment, Past Due [Line Items]
31-59 Days Past Due	8,094	13,555
60-89 Days Past Due	2,212	2,474
>90 Days Past Due and Accruing	3,988	3,711
Non-accrual	11,083	13,272
Total >90 Days	15,071	16,983
Total Past Due	25,377	33,012
Current	1,707,659	1,731,185
Loans, net of unearned income	1,733,036	1,764,197	1,773,554
Real-estate - residential mortgage [Member]
Financial Receivable, Recorded investment, Past Due [Line Items]
31-59 Days Past Due	17,102	16,969
60-89 Days Past Due	7,794	6,310
>90 Days Past Due and Accruing	6,285	9,065
Non-accrual	21,850	22,282
Total >90 Days	28,135	31,347
Total Past Due	53,031	54,626
Current	1,319,002	1,282,754
Loans, net of unearned income	1,372,033	1,337,380	1,327,469
Construction - Commercial Residential [Member]
Financial Receivable, Recorded investment, Past Due [Line Items]
31-59 Days Past Due	215	0
60-89 Days Past Due	0	645
>90 Days Past Due and Accruing	205	346
Non-accrual	17,500	18,202
Total >90 Days	17,705	18,548
Total Past Due	17,920	19,193
Current	223,499	216,176
Loans, net of unearned income	241,419	235,369
Construction - Commercial [Member]
Financial Receivable, Recorded investment, Past Due [Line Items]
31-59 Days Past Due	0	14
60-89 Days Past Due	0	0
>90 Days Past Due and Accruing	0	0
Non-accrual	1,874	2,171
Total >90 Days	1,874	2,171
Total Past Due	1,874	2,185
Current	375,332	267,312
Loans, net of unearned income	377,206	269,497
Construction other [Member]
Financial Receivable, Recorded investment, Past Due [Line Items]
31-59 Days Past Due	0	0
60-89 Days Past Due	0	0
>90 Days Past Due and Accruing	0	0
Non-accrual	281	548
Total >90 Days	281	548
Total Past Due	281	548
Current	68,822	68,258
Loans, net of unearned income	69,103	68,806
Consumer [Member]
Financial Receivable, Recorded investment, Past Due [Line Items]
31-59 Days Past Due	3,847	4,955
60-89 Days Past Due	1,381	1,943
>90 Days Past Due and Accruing	2,515	2,541
Non-accrual	0	2
Total >90 Days	2,515	2,543
Total Past Due	7,743	9,441
Current	270,476	273,683
Loans, net of unearned income	278,219	283,124	296,142
Consumer - direct [Member]
Financial Receivable, Recorded investment, Past Due [Line Items]
31-59 Days Past Due	2,032	2,091
60-89 Days Past Due	993	1,495
>90 Days Past Due and Accruing	2,359	2,391
Non-accrual	0	0
Total >90 Days	2,359	2,391
Total Past Due	5,384	5,977
Current	115,449	126,666
Loans, net of unearned income	120,833	132,643
Consumer - Indirect [Member]
Financial Receivable, Recorded investment, Past Due [Line Items]
31-59 Days Past Due	1,815	2,864
60-89 Days Past Due	388	448
>90 Days Past Due and Accruing	156	150
Non-accrual	0	2
Total >90 Days	156	152
Total Past Due	2,359	3,464
Current	155,027	147,017
Loans, net of unearned income	157,386	150,481
Leasing and other and overdrafts [Member]
Financial Receivable, Recorded investment, Past Due [Line Items]
31-59 Days Past Due	185	559
60-89 Days Past Due	84	22
>90 Days Past Due and Accruing	388	48
Non-accrual	0	0
Total >90 Days	388	48
Total Past Due	657	629
Current	110,491	92,876
Loans, net of unearned income	$ 111,148	$ 93,505	$ 97,749