Loans and Allowance for Credit Losses Summary of Delinquency and Non-Performing Status by Portfolio Segment (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2019 USD ($) day	Dec. 31, 2018 USD ($)	Mar. 31, 2018 USD ($)
Financing Receivable, Impaired [Line Items]
Loans and leases, net of unearned income	$ 16,262,633	$ 16,165,800	$ 15,696,284
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 and leases, net of unearned income	$ 1,413,500	1,452,137	1,514,241
Real-estate - home equity | Performing
Financing Receivable, Impaired [Line Items]
Loans and leases, net of unearned income	1,391,323	1,431,666
Real-estate - home equity | Delinquent
Financing Receivable, Impaired [Line Items]
Loans and leases, net of unearned income	11,682	10,702
Real-estate - home equity | Non-performing
Financing Receivable, Impaired [Line Items]
Loans and leases, net of unearned income	10,495	9,769
Real estate - residential mortgage
Financing Receivable, Impaired [Line Items]
Loans and leases, net of unearned income	2,313,908	2,251,044	1,976,524
Real estate - residential mortgage | Performing
Financing Receivable, Impaired [Line Items]
Loans and leases, net of unearned income	2,270,802	2,202,955
Real estate - residential mortgage | Delinquent
Financing Receivable, Impaired [Line Items]
Loans and leases, net of unearned income	20,807	28,988
Real estate - residential mortgage | Non-performing
Financing Receivable, Impaired [Line Items]
Loans and leases, net of unearned income	22,299	19,101
Construction - other
Financing Receivable, Impaired [Line Items]
Loans and leases, net of unearned income	76,966	72,001
Construction - other | Performing
Financing Receivable, Impaired [Line Items]
Loans and leases, net of unearned income	76,628	71,511
Construction - other | Delinquent
Financing Receivable, Impaired [Line Items]
Loans and leases, net of unearned income	140	0
Construction - other | Non-performing
Financing Receivable, Impaired [Line Items]
Loans and leases, net of unearned income	198	490
Consumer
Financing Receivable, Impaired [Line Items]
Loans and leases, net of unearned income	53,638	56,033
Consumer | Performing
Financing Receivable, Impaired [Line Items]
Loans and leases, net of unearned income	53,283	55,629
Consumer | Delinquent
Financing Receivable, Impaired [Line Items]
Loans and leases, net of unearned income	251	338
Consumer | Non-performing
Financing Receivable, Impaired [Line Items]
Loans and leases, net of unearned income	104	66
Consumer - indirect
Financing Receivable, Impaired [Line Items]
Loans and leases, net of unearned income	379,907	363,153
Consumer - indirect | Performing
Financing Receivable, Impaired [Line Items]
Loans and leases, net of unearned income	376,538	359,405
Consumer - indirect | Delinquent
Financing Receivable, Impaired [Line Items]
Loans and leases, net of unearned income	3,198	3,405
Consumer - indirect | Non-performing
Financing Receivable, Impaired [Line Items]
Loans and leases, net of unearned income	171	343
Consumer
Financing Receivable, Impaired [Line Items]
Loans and leases, net of unearned income	433,545	419,186	326,766
Consumer | Performing
Financing Receivable, Impaired [Line Items]
Loans and leases, net of unearned income	429,821	415,034
Consumer | Delinquent
Financing Receivable, Impaired [Line Items]
Loans and leases, net of unearned income	3,449	3,743
Consumer | Non-performing
Financing Receivable, Impaired [Line Items]
Loans and leases, net of unearned income	275	409
Equipment lease financing, other and overdrafts
Financing Receivable, Impaired [Line Items]
Loans and leases, net of unearned income	290,367	288,001	$ 271,042
Equipment lease financing, other and overdrafts | Performing
Financing Receivable, Impaired [Line Items]
Loans and leases, net of unearned income	270,165	267,112
Equipment lease financing, other and overdrafts | Delinquent
Financing Receivable, Impaired [Line Items]
Loans and leases, net of unearned income	1,594	1,302
Equipment lease financing, other and overdrafts | Non-performing
Financing Receivable, Impaired [Line Items]
Loans and leases, net of unearned income	18,608	19,587
Real Estate, Consumer, Leasing And Other Loans [Member] [Member]
Financing Receivable, Impaired [Line Items]
Loans and leases, net of unearned income	4,528,286	4,482,369
Real Estate, Consumer, Leasing And Other Loans [Member] [Member] | Performing
Financing Receivable, Impaired [Line Items]
Loans and leases, net of unearned income	4,438,739	4,388,278
Real Estate, Consumer, Leasing And Other Loans [Member] [Member] | Delinquent
Financing Receivable, Impaired [Line Items]
Loans and leases, net of unearned income	37,672	44,735
Real Estate, Consumer, Leasing And Other Loans [Member] [Member] | Non-performing
Financing Receivable, Impaired [Line Items]
Loans and leases, net of unearned income	$ 51,875	$ 49,356
Commercial Loans, Commerical Mortgages, Constructions Loans
Financing Receivable, Impaired [Line Items]
% of Total	100.00%	100.00%
Commercial Loans, Commerical Mortgages, Constructions Loans | Performing
Financing Receivable, Impaired [Line Items]
% of Total	98.00%	97.90%
Commercial Loans, Commerical Mortgages, Constructions Loans | Delinquent
Financing Receivable, Impaired [Line Items]
% of Total	0.80%	1.00%
Commercial Loans, Commerical Mortgages, Constructions Loans | Non-performing
Financing Receivable, Impaired [Line Items]
% of Total	1.20%	1.10%