Loans and Allowance for Credit Losses Summary of Delinquency and Non-Performing Status by Portfolio Segment (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Mar. 31, 2015 USD ($)
Financing Receivable, Impaired [Line Items]
Loans, net of unearned income	$ 13,870,701	$ 13,838,602	$ 13,115,505
Real-estate - home equity [Member]
Financing Receivable, Impaired [Line Items]
Loans, net of unearned income	1,659,481	1,684,439	1,701,623
Real-estate - residential mortgage [Member]
Financing Receivable, Impaired [Line Items]
Loans, net of unearned income	1,377,459	1,376,160	1,364,788
Construction other [Member]
Financing Receivable, Impaired [Line Items]
Loans, net of unearned income	61,777	60,694
Consumer [Member]
Financing Receivable, Impaired [Line Items]
Loans, net of unearned income	263,221	268,588	257,301
Consumer - direct [Member]
Financing Receivable, Impaired [Line Items]
Loans, net of unearned income	93,463	98,719
Consumer - Indirect [Member]
Financing Receivable, Impaired [Line Items]
Loans, net of unearned income	169,758	169,869
Leasing and other and overdrafts [Member]
Financing Receivable, Impaired [Line Items]
Loans, net of unearned income	166,227	158,135	$ 124,255
Real Estate, Home Equity, Construction, Other, Consumer and Leasing [Member]
Financing Receivable, Impaired [Line Items]
Loans, net of unearned income	3,528,165	3,548,016
Commercial Loans, Commerical Mortgages, Constructions Loans [Member]
Financing Receivable, Impaired [Line Items]
Loans, net of unearned income	$ 10,342,536	$ 10,290,586
Loans And Leases Receivable Percentage Of Loans Within Delinquecy Category By Total Non Risk Rated Loans	100.00%	100.00%
Performing Financing Receivable [Member] | Real-estate - home equity [Member]
Financing Receivable, Impaired [Line Items]
Loans, net of unearned income	$ 1,636,040	$ 1,660,773
Performing Financing Receivable [Member] | Real-estate - residential mortgage [Member]
Financing Receivable, Impaired [Line Items]
Loans, net of unearned income	1,334,744	1,329,371
Performing Financing Receivable [Member] | Construction other [Member]
Financing Receivable, Impaired [Line Items]
Loans, net of unearned income	60,481	59,997
Performing Financing Receivable [Member] | Consumer [Member]
Financing Receivable, Impaired [Line Items]
Loans, net of unearned income	258,067	261,085
Performing Financing Receivable [Member] | Consumer - direct [Member]
Financing Receivable, Impaired [Line Items]
Loans, net of unearned income	90,204	94,262
Performing Financing Receivable [Member] | Consumer - Indirect [Member]
Financing Receivable, Impaired [Line Items]
Loans, net of unearned income	167,863	166,823
Performing Financing Receivable [Member] | Leasing and other and overdrafts [Member]
Financing Receivable, Impaired [Line Items]
Loans, net of unearned income	164,002	155,870
Performing Financing Receivable [Member] | Real Estate, Home Equity, Construction, Other, Consumer and Leasing [Member]
Financing Receivable, Impaired [Line Items]
Loans, net of unearned income	$ 3,453,334	$ 3,467,096
Performing Financing Receivable [Member] | Commercial Loans, Commerical Mortgages, Constructions Loans [Member]
Financing Receivable, Impaired [Line Items]
Loans And Leases Receivable Percentage Of Loans Within Delinquecy Category By Total Non Risk Rated Loans	97.90%	97.70%
Delinquent [Member] | Real-estate - home equity [Member]
Financing Receivable, Impaired [Line Items]
Loans, net of unearned income	$ 9,033	$ 8,983
Delinquent [Member] | Real-estate - residential mortgage [Member]
Financing Receivable, Impaired [Line Items]
Loans, net of unearned income	17,533	18,305
Delinquent [Member] | Construction other [Member]
Financing Receivable, Impaired [Line Items]
Loans, net of unearned income	686	88
Delinquent [Member] | Consumer [Member]
Financing Receivable, Impaired [Line Items]
Loans, net of unearned income	3,352	5,063
Delinquent [Member] | Consumer - direct [Member]
Financing Receivable, Impaired [Line Items]
Loans, net of unearned income	1,662	2,254
Delinquent [Member] | Consumer - Indirect [Member]
Financing Receivable, Impaired [Line Items]
Loans, net of unearned income	1,690	2,809
Delinquent [Member] | Leasing and other and overdrafts [Member]
Financing Receivable, Impaired [Line Items]
Loans, net of unearned income	711	759
Delinquent [Member] | Real Estate, Home Equity, Construction, Other, Consumer and Leasing [Member]
Financing Receivable, Impaired [Line Items]
Loans, net of unearned income	$ 31,315	$ 33,198
Delinquent [Member] | Commercial Loans, Commerical Mortgages, Constructions Loans [Member]
Financing Receivable, Impaired [Line Items]
Loans And Leases Receivable Percentage Of Loans Within Delinquecy Category By Total Non Risk Rated Loans	0.90%	1.00%
Nonperforming Financing Receivable [Member]
Financing Receivable, Impaired [Line Items]
Days past due	90
Nonperforming Financing Receivable [Member] | Real-estate - home equity [Member]
Financing Receivable, Impaired [Line Items]
Loans, net of unearned income	$ 14,408	$ 14,683
Nonperforming Financing Receivable [Member] | Real-estate - residential mortgage [Member]
Financing Receivable, Impaired [Line Items]
Loans, net of unearned income	25,182	28,484
Nonperforming Financing Receivable [Member] | Construction other [Member]
Financing Receivable, Impaired [Line Items]
Loans, net of unearned income	610	609
Nonperforming Financing Receivable [Member] | Consumer [Member]
Financing Receivable, Impaired [Line Items]
Loans, net of unearned income	1,802	2,440
Nonperforming Financing Receivable [Member] | Consumer - direct [Member]
Financing Receivable, Impaired [Line Items]
Loans, net of unearned income	1,597	2,203
Nonperforming Financing Receivable [Member] | Consumer - Indirect [Member]
Financing Receivable, Impaired [Line Items]
Loans, net of unearned income	205	237
Nonperforming Financing Receivable [Member] | Leasing and other and overdrafts [Member]
Financing Receivable, Impaired [Line Items]
Loans, net of unearned income	1,514	1,506
Nonperforming Financing Receivable [Member] | Real Estate, Home Equity, Construction, Other, Consumer and Leasing [Member]
Financing Receivable, Impaired [Line Items]
Loans, net of unearned income	$ 43,516	$ 47,722
Nonperforming Financing Receivable [Member] | Commercial Loans, Commerical Mortgages, Constructions Loans [Member]
Financing Receivable, Impaired [Line Items]
Loans And Leases Receivable Percentage Of Loans Within Delinquecy Category By Total Non Risk Rated Loans	1.20%	1.30%
Minimum [Member] | Delinquent [Member]
Financing Receivable, Impaired [Line Items]
Days past due	30
Maximum [Member] | Delinquent [Member]
Financing Receivable, Impaired [Line Items]
Days past due	89