Loans and Allowance for Credit Losses Past Due Loan Status and Non-Accrual Loans by Portfolio Segment (Details) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014	Jun. 30, 2014
Financial Receivable, Recorded investment, Past Due [Line Items]
31-59 Days Past Due	$ 51,428	$ 51,177
60-89 Days Past Due	10,503	17,169
>90 Days Past Due and Accruing	20,353	17,402
Non-accrual	129,152	121,080
Total >90 Days	149,505	138,482
Total Past Due	211,436	206,828
Current	13,032,794	12,904,888
Loans, net of unearned income	13,244,230	13,111,716	$ 12,839,511
Real-estate commercial mortage [Member]
Financial Receivable, Recorded investment, Past Due [Line Items]
31-59 Days Past Due	16,139	14,399
60-89 Days Past Due	1,848	3,677
>90 Days Past Due and Accruing	1,947	800
Non-accrual	47,985	44,437
Total >90 Days	49,932	45,237
Total Past Due	67,919	63,313
Current	5,169,881	5,133,842
Loans, net of unearned income	5,237,800	5,197,155	5,128,734
Commercial - industrial, financial, and agricultural [Member]
Financial Receivable, Recorded investment, Past Due [Line Items]
31-59 Days Past Due	6,796	5,234
60-89 Days Past Due	1,543	1,023
>90 Days Past Due and Accruing	730	619
Non-accrual	35,109	29,769
Total >90 Days	35,839	30,388
Total Past Due	44,178	36,645
Current	3,762,521	3,688,922
Loans, net of unearned income	3,806,699	3,725,567	3,601,721
Commercial - Secured [Member]
Financial Receivable, Recorded investment, Past Due [Line Items]
31-59 Days Past Due	6,489	4,839
60-89 Days Past Due	1,463	958
>90 Days Past Due and Accruing	730	610
Non-accrual	32,379	28,747
Total >90 Days	33,109	29,357
Total Past Due	41,061	35,154
Current	3,612,599	3,529,460
Loans, net of unearned income	3,653,660	3,564,614
Commercial - unsecured [Member]
Financial Receivable, Recorded investment, Past Due [Line Items]
31-59 Days Past Due	307	395
60-89 Days Past Due	80	65
>90 Days Past Due and Accruing	0	9
Non-accrual	2,730	1,022
Total >90 Days	2,730	1,031
Total Past Due	3,117	1,491
Current	149,922	159,462
Loans, net of unearned income	153,039	160,953
Real-estate - construction [Member]
Financial Receivable, Recorded investment, Past Due [Line Items]
31-59 Days Past Due	151	160
60-89 Days Past Due	0	0
>90 Days Past Due and Accruing	416	51
Non-accrual	14,468	16,348
Total >90 Days	14,884	16,399
Total Past Due	15,035	16,559
Current	716,890	674,042
Loans, net of unearned income	731,925	690,601	634,018
Real-estate - home equity [Member]
Financial Receivable, Recorded investment, Past Due [Line Items]
31-59 Days Past Due	7,161	8,048
60-89 Days Past Due	2,124	2,883
>90 Days Past Due and Accruing	4,653	4,257
Non-accrual	9,979	10,483
Total >90 Days	14,632	14,740
Total Past Due	23,917	25,671
Current	1,665,771	1,711,017
Loans, net of unearned income	1,689,688	1,736,688	1,730,497
Real-estate - residential mortgage [Member]
Financial Receivable, Recorded investment, Past Due [Line Items]
31-59 Days Past Due	16,835	18,789
60-89 Days Past Due	4,056	8,145
>90 Days Past Due and Accruing	9,951	8,952
Non-accrual	21,611	20,043
Total >90 Days	31,562	28,995
Total Past Due	52,453	55,929
Current	1,316,650	1,321,139
Loans, net of unearned income	1,369,103	1,377,068	1,361,976
Construction - Commercial Residential [Member]
Financial Receivable, Recorded investment, Past Due [Line Items]
31-59 Days Past Due	151	160
60-89 Days Past Due	0	0
>90 Days Past Due and Accruing	0	0
Non-accrual	11,689	13,463
Total >90 Days	11,689	13,463
Total Past Due	11,840	13,623
Current	175,108	190,047
Loans, net of unearned income	186,948	203,670
Construction - Commercial [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	2,498	2,604
Total >90 Days	2,498	2,604
Total Past Due	2,498	2,604
Current	485,918	424,815
Loans, net of unearned income	488,416	427,419
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	416	51
Non-accrual	281	281
Total >90 Days	697	332
Total Past Due	697	332
Current	55,864	59,180
Loans, net of unearned income	56,561	59,512
Consumer [Member]
Financial Receivable, Recorded investment, Past Due [Line Items]
31-59 Days Past Due	3,878	4,190
60-89 Days Past Due	847	1,275
>90 Days Past Due and Accruing	2,583	2,590
Non-accrual	0	0
Total >90 Days	2,583	2,590
Total Past Due	7,308	8,055
Current	265,186	257,376
Loans, net of unearned income	272,494	265,431	280,557
Consumer - direct [Member]
Financial Receivable, Recorded investment, Past Due [Line Items]
31-59 Days Past Due	2,159	2,034
60-89 Days Past Due	727	857
>90 Days Past Due and Accruing	2,326	2,414
Non-accrual	0	0
Total >90 Days	2,326	2,414
Total Past Due	5,212	5,305
Current	103,985	104,018
Loans, net of unearned income	109,197	109,323
Consumer - Indirect [Member]
Financial Receivable, Recorded investment, Past Due [Line Items]
31-59 Days Past Due	1,719	2,156
60-89 Days Past Due	120	418
>90 Days Past Due and Accruing	257	176
Non-accrual	0	0
Total >90 Days	257	176
Total Past Due	2,096	2,750
Current	161,201	153,358
Loans, net of unearned income	163,297	156,108
Leasing and other and overdrafts [Member]
Financial Receivable, Recorded investment, Past Due [Line Items]
31-59 Days Past Due	468	357
60-89 Days Past Due	85	166
>90 Days Past Due and Accruing	73	133
Non-accrual	0	0
Total >90 Days	73	133
Total Past Due	626	656
Current	135,895	118,550
Loans, net of unearned income	$ 136,521	$ 119,206	$ 102,008