Loans and Leases (Commercial, Commercial Real Estate Loans And Equipment Financing Loans Segregated By Risk Rating Exposure) (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Financing Receivable, Impaired [Line Items]
Total Loans and Leases	$ 20,036,986	$ 18,465,489	$ 17,523,858
Commercial Portfolio Segment [Member]
Financing Receivable, Impaired [Line Items]
Total Loans and Leases	6,343,497	6,216,606	5,368,694
Commercial Portfolio Segment [Member] | (1) - (6) Pass [Member]
Financing Receivable, Impaired [Line Items]
Total Loans and Leases	5,985,338	5,781,138
Commercial Portfolio Segment [Member] | (7) Special Mention [Member]
Financing Receivable, Impaired [Line Items]
Total Loans and Leases	94,809	206,351
Commercial Portfolio Segment [Member] | (8) Substandard [Member]
Financing Receivable, Impaired [Line Items]
Total Loans and Leases	259,490	222,405
Commercial Portfolio Segment [Member] | (9) Doubtful [Member]
Financing Receivable, Impaired [Line Items]
Total Loans and Leases	3,860	6,712
Commercial Real Estate Portfolio Segment [Member]
Financing Receivable, Impaired [Line Items]
Total Loans and Leases	5,949,339	4,927,145	4,523,828
Commercial Real Estate Portfolio Segment [Member] | (1) - (6) Pass [Member]
Financing Receivable, Impaired [Line Items]
Total Loans and Leases	5,860,981	4,773,298
Commercial Real Estate Portfolio Segment [Member] | (7) Special Mention [Member]
Financing Receivable, Impaired [Line Items]
Total Loans and Leases	26,978	75,338
Commercial Real Estate Portfolio Segment [Member] | (8) Substandard [Member]
Financing Receivable, Impaired [Line Items]
Total Loans and Leases	61,380	78,509
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	537,341	508,397	$ 550,233
Finance Leases Portfolio Segment [Member] | (1) - (6) Pass [Member]
Financing Receivable, Impaired [Line Items]
Total Loans and Leases	528,561	494,585
Finance Leases Portfolio Segment [Member] | (7) Special Mention [Member]
Financing Receivable, Impaired [Line Items]
Total Loans and Leases	808	1,303
Finance Leases Portfolio Segment [Member] | (8) Substandard [Member]
Financing Receivable, Impaired [Line Items]
Total Loans and Leases	7,972	12,509
Finance Leases Portfolio Segment [Member] | (9) Doubtful [Member]
Financing Receivable, Impaired [Line Items]
Total Loans and Leases	$ 0	$ 0