Loans and Leases (Commercial, Commercial Real Estate Loans And Equipment Financing Loans Segregated By Risk Rating Exposure) (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Financing Receivable, Impaired [Line Items]
Total Loans and Leases	$ 17,523,858	$ 17,026,588	$ 15,671,735
Commercial Portfolio Segment [Member]
Financing Receivable, Impaired [Line Items]
Total Loans and Leases	5,368,694	4,940,931	4,315,999
Commercial Portfolio Segment [Member] | (1) - (6) Pass [Member]
Financing Receivable, Impaired [Line Items]
Total Loans and Leases	5,048,162	4,655,007
Commercial Portfolio Segment [Member] | (7) Special Mention [Member]
Financing Receivable, Impaired [Line Items]
Total Loans and Leases	104,594	56,240
Commercial Portfolio Segment [Member] | (8) Substandard [Member]
Financing Receivable, Impaired [Line Items]
Total Loans and Leases	206,883	226,603
Commercial Portfolio Segment [Member] | (9) Doubtful [Member]
Financing Receivable, Impaired [Line Items]
Total Loans and Leases	9,055	3,081
Commercial Real Estate Portfolio Segment [Member]
Financing Receivable, Impaired [Line Items]
Total Loans and Leases	4,523,828	4,510,846	3,991,649
Commercial Real Estate Portfolio Segment [Member] | (1) - (6) Pass [Member]
Financing Receivable, Impaired [Line Items]
Total Loans and Leases	4,355,916	4,357,458
Commercial Real Estate Portfolio Segment [Member] | (7) Special Mention [Member]
Financing Receivable, Impaired [Line Items]
Total Loans and Leases	62,065	69,023
Commercial Real Estate Portfolio Segment [Member] | (8) Substandard [Member]
Financing Receivable, Impaired [Line Items]
Total Loans and Leases	105,847	84,365
Commercial Real Estate Portfolio Segment [Member] | (9) Doubtful [Member]
Financing Receivable, Impaired [Line Items]
Total Loans and Leases	0	0
Finance Leases Portfolio Segment [Member]
Financing Receivable, Impaired [Line Items]
Total Loans and Leases	550,233	635,629	$ 600,526
Finance Leases Portfolio Segment [Member] | (1) - (6) Pass [Member]
Financing Receivable, Impaired [Line Items]
Total Loans and Leases	525,105	618,084
Finance Leases Portfolio Segment [Member] | (7) Special Mention [Member]
Financing Receivable, Impaired [Line Items]
Total Loans and Leases	8,022	1,324
Finance Leases Portfolio Segment [Member] | (8) Substandard [Member]
Financing Receivable, Impaired [Line Items]
Total Loans and Leases	17,106	16,221
Finance Leases Portfolio Segment [Member] | (9) Doubtful [Member]
Financing Receivable, Impaired [Line Items]
Total Loans and Leases	$ 0	$ 0