Loans and Allowance for Credit Losses Summary of Delinquency and Non-Performing Status by Portfolio Segment (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2017 USD ($) day	Dec. 31, 2016 USD ($)	Jun. 30, 2016 USD ($)
Financing Receivable, Impaired [Line Items]
Loans, net of unearned income	$ 15,346,617	$ 14,699,272	$ 14,155,159
Delinquent | Minimum
Financing Receivable, Impaired [Line Items]
Days past due | day	30
Delinquent | Maximum
Financing Receivable, Impaired [Line Items]
Days past due | day	89
Non-performing
Financing Receivable, Impaired [Line Items]
Days past due | day	90
Real-estate - home equity
Financing Receivable, Impaired [Line Items]
Loans, net of unearned income	$ 1,579,739	1,625,115	1,647,319
Real-estate - home equity | Performing
Financing Receivable, Impaired [Line Items]
Loans, net of unearned income	1,557,629	1,602,687
Real-estate - home equity | Delinquent
Financing Receivable, Impaired [Line Items]
Loans, net of unearned income	10,223	9,274
Real-estate - home equity | Non-performing
Financing Receivable, Impaired [Line Items]
Loans, net of unearned income	11,887	13,154
Real estate - residential mortgage
Financing Receivable, Impaired [Line Items]
Loans, net of unearned income	1,784,712	1,601,994	1,447,292
Real estate - residential mortgage | Performing
Financing Receivable, Impaired [Line Items]
Loans, net of unearned income	1,746,977	1,557,995
Real estate - residential mortgage | Delinquent
Financing Receivable, Impaired [Line Items]
Loans, net of unearned income	15,889	20,344
Real estate - residential mortgage | Non-performing
Financing Receivable, Impaired [Line Items]
Loans, net of unearned income	21,846	23,655
Construction - other
Financing Receivable, Impaired [Line Items]
Loans, net of unearned income	52,960	56,970
Construction - other | Performing
Financing Receivable, Impaired [Line Items]
Loans, net of unearned income	51,869	55,874
Construction - other | Delinquent
Financing Receivable, Impaired [Line Items]
Loans, net of unearned income	0	0
Construction - other | Non-performing
Financing Receivable, Impaired [Line Items]
Loans, net of unearned income	1,091	1,096
Consumer - direct
Financing Receivable, Impaired [Line Items]
Loans, net of unearned income	58,729	96,887
Consumer - direct | Performing
Financing Receivable, Impaired [Line Items]
Loans, net of unearned income	55,825	93,572
Consumer - direct | Delinquent
Financing Receivable, Impaired [Line Items]
Loans, net of unearned income	1,761	1,752
Consumer - direct | Non-performing
Financing Receivable, Impaired [Line Items]
Loans, net of unearned income	1,143	1,563
Consumer - indirect
Financing Receivable, Impaired [Line Items]
Loans, net of unearned income	224,427	194,583
Consumer - indirect | Performing
Financing Receivable, Impaired [Line Items]
Loans, net of unearned income	222,380	190,656
Consumer - indirect | Delinquent
Financing Receivable, Impaired [Line Items]
Loans, net of unearned income	1,921	3,599
Consumer - indirect | Non-performing
Financing Receivable, Impaired [Line Items]
Loans, net of unearned income	126	328
Consumer
Financing Receivable, Impaired [Line Items]
Loans, net of unearned income	283,156	291,470	278,071
Consumer | Performing
Financing Receivable, Impaired [Line Items]
Loans, net of unearned income	278,205	284,228
Consumer | Delinquent
Financing Receivable, Impaired [Line Items]
Loans, net of unearned income	3,682	5,351
Consumer | Non-performing
Financing Receivable, Impaired [Line Items]
Loans, net of unearned income	1,269	1,891
Leasing, other and overdrafts
Financing Receivable, Impaired [Line Items]
Loans, net of unearned income	252,253	230,976	$ 194,254
Leasing, other and overdrafts | Performing
Financing Receivable, Impaired [Line Items]
Loans, net of unearned income	251,050	229,591
Leasing, other and overdrafts | Delinquent
Financing Receivable, Impaired [Line Items]
Loans, net of unearned income	922	1,068
Leasing, other and overdrafts | Non-performing
Financing Receivable, Impaired [Line Items]
Loans, net of unearned income	281	317
Commercial Loans, Commerical Mortgages, Constructions Loans
Financing Receivable, Impaired [Line Items]
Loans, net of unearned income	$ 3,952,820	$ 3,806,525
% of Total	100.00%	100.00%
Commercial Loans, Commerical Mortgages, Constructions Loans | Performing
Financing Receivable, Impaired [Line Items]
Loans, net of unearned income	$ 3,885,730	$ 3,730,375
% of Total	98.30%	98.00%
Commercial Loans, Commerical Mortgages, Constructions Loans | Delinquent
Financing Receivable, Impaired [Line Items]
Loans, net of unearned income	$ 30,716	$ 36,037
% of Total	0.80%	0.90%
Commercial Loans, Commerical Mortgages, Constructions Loans | Non-performing
Financing Receivable, Impaired [Line Items]
Loans, net of unearned income	$ 36,374	$ 40,113
% of Total	0.90%	1.10%