Loans and Allowance for Credit Losses Summary of Delinquency and Non-Performing Status by Portfolio Segment (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2016 USD ($) day	Dec. 31, 2015 USD ($)	Sep. 30, 2015 USD ($)
Financing Receivable, Impaired [Line Items]
Loans, net of unearned income	$ 14,391,238	$ 13,838,602	$ 13,536,361
Real-estate - home equity [Member]
Financing Receivable, Impaired [Line Items]
Loans, net of unearned income	1,640,421	1,684,439	1,693,649
Real-estate - residential mortgage [Member]
Financing Receivable, Impaired [Line Items]
Loans, net of unearned income	1,542,696	1,376,160	1,382,085
Construction other [Member]
Financing Receivable, Impaired [Line Items]
Loans, net of unearned income	62,834	60,694
Consumer [Member]
Financing Receivable, Impaired [Line Items]
Loans, net of unearned income	283,673	268,588	271,696
Consumer - direct [Member]
Financing Receivable, Impaired [Line Items]
Loans, net of unearned income	94,782	98,719
Consumer - Indirect [Member]
Financing Receivable, Impaired [Line Items]
Loans, net of unearned income	188,891	169,869
Leasing and other and overdrafts [Member]
Financing Receivable, Impaired [Line Items]
Loans, net of unearned income	219,780	158,135	$ 149,530
Real Estate, Home Equity, Construction, Other, Consumer and Leasing [Member]
Financing Receivable, Impaired [Line Items]
Loans, net of unearned income	3,749,404	3,548,016
Commercial Loans, Commerical Mortgages, Constructions Loans [Member]
Financing Receivable, Impaired [Line Items]
Loans, net of unearned income	$ 10,641,834	$ 10,290,586
% of Total	100.00%	100.00%
Performing Financing Receivable [Member] | Real-estate - home equity [Member]
Financing Receivable, Impaired [Line Items]
Loans, net of unearned income	$ 1,615,657	$ 1,660,773
Performing Financing Receivable [Member] | Real-estate - residential mortgage [Member]
Financing Receivable, Impaired [Line Items]
Loans, net of unearned income	1,501,486	1,329,371
Performing Financing Receivable [Member] | Construction other [Member]
Financing Receivable, Impaired [Line Items]
Loans, net of unearned income	61,738	59,997
Performing Financing Receivable [Member] | Consumer [Member]
Financing Receivable, Impaired [Line Items]
Loans, net of unearned income	277,037	261,085
Performing Financing Receivable [Member] | Consumer - direct [Member]
Financing Receivable, Impaired [Line Items]
Loans, net of unearned income	91,164	94,262
Performing Financing Receivable [Member] | Consumer - Indirect [Member]
Financing Receivable, Impaired [Line Items]
Loans, net of unearned income	185,873	166,823
Performing Financing Receivable [Member] | Leasing and other and overdrafts [Member]
Financing Receivable, Impaired [Line Items]
Loans, net of unearned income	218,275	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	$ 3,674,193	$ 3,467,096
Performing Financing Receivable [Member] | Commercial Loans, Commerical Mortgages, Constructions Loans [Member]
Financing Receivable, Impaired [Line Items]
% of Total	98.00%	97.70%
Delinquent [Member] | Real-estate - home equity [Member]
Financing Receivable, Impaired [Line Items]
Loans, net of unearned income	$ 10,504	$ 8,983
Delinquent [Member] | Real-estate - residential mortgage [Member]
Financing Receivable, Impaired [Line Items]
Loans, net of unearned income	17,759	18,305
Delinquent [Member] | Construction other [Member]
Financing Receivable, Impaired [Line Items]
Loans, net of unearned income	0	88
Delinquent [Member] | Consumer [Member]
Financing Receivable, Impaired [Line Items]
Loans, net of unearned income	4,470	5,063
Delinquent [Member] | Consumer - direct [Member]
Financing Receivable, Impaired [Line Items]
Loans, net of unearned income	1,675	2,254
Delinquent [Member] | Consumer - Indirect [Member]
Financing Receivable, Impaired [Line Items]
Loans, net of unearned income	2,795	2,809
Delinquent [Member] | Leasing and other and overdrafts [Member]
Financing Receivable, Impaired [Line Items]
Loans, net of unearned income	1,454	759
Delinquent [Member] | Real Estate, Home Equity, Construction, Other, Consumer and Leasing [Member]
Financing Receivable, Impaired [Line Items]
Loans, net of unearned income	$ 34,187	$ 33,198
Delinquent [Member] | Commercial Loans, Commerical Mortgages, Constructions Loans [Member]
Financing Receivable, Impaired [Line Items]
% of Total	0.90%	1.00%
Nonperforming Financing Receivable [Member]
Financing Receivable, Impaired [Line Items]
Days past due | day	90
Nonperforming Financing Receivable [Member] | Real-estate - home equity [Member]
Financing Receivable, Impaired [Line Items]
Loans, net of unearned income	$ 14,260	$ 14,683
Nonperforming Financing Receivable [Member] | Real-estate - residential mortgage [Member]
Financing Receivable, Impaired [Line Items]
Loans, net of unearned income	23,451	28,484
Nonperforming Financing Receivable [Member] | Construction other [Member]
Financing Receivable, Impaired [Line Items]
Loans, net of unearned income	1,096	609
Nonperforming Financing Receivable [Member] | Consumer [Member]
Financing Receivable, Impaired [Line Items]
Loans, net of unearned income	2,166	2,440
Nonperforming Financing Receivable [Member] | Consumer - direct [Member]
Financing Receivable, Impaired [Line Items]
Loans, net of unearned income	1,943	2,203
Nonperforming Financing Receivable [Member] | Consumer - Indirect [Member]
Financing Receivable, Impaired [Line Items]
Loans, net of unearned income	223	237
Nonperforming Financing Receivable [Member] | Leasing and other and overdrafts [Member]
Financing Receivable, Impaired [Line Items]
Loans, net of unearned income	51	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	$ 41,024	$ 47,722
Nonperforming Financing Receivable [Member] | Commercial Loans, Commerical Mortgages, Constructions Loans [Member]
Financing Receivable, Impaired [Line Items]
% of Total	1.10%	1.30%
Minimum [Member] | Delinquent [Member]
Financing Receivable, Impaired [Line Items]
Days past due | day	30
Maximum [Member] | Delinquent [Member]
Financing Receivable, Impaired [Line Items]
Days past due | day	89