Loans and Leases (Commercial, Commercial Real Estate Loans And Equipment Financing Loans Segregated By Risk Rating Exposure) (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Financing Receivable, Impaired [Line Items]
Total Loans and Leases	$ 21,641,215	$ 20,036,986	$ 18,465,489
Commercial Non-Real Estate Portfolio Segment
Financing Receivable, Impaired [Line Items]
Total Loans and Leases		6,343,497
Commercial Non-Real Estate Portfolio Segment | (1) - (6) Pass [Member]
Financing Receivable, Impaired [Line Items]
Total Loans and Leases		5,985,338
Commercial Non-Real Estate Portfolio Segment | (7) Special Mention [Member]
Financing Receivable, Impaired [Line Items]
Total Loans and Leases		94,809
Commercial Non-Real Estate Portfolio Segment | (8) Substandard [Member]
Financing Receivable, Impaired [Line Items]
Total Loans and Leases		259,490
Commercial Non-Real Estate Portfolio Segment | (9) Doubtful [Member]
Financing Receivable, Impaired [Line Items]
Total Loans and Leases		3,860
Commercial Real Estate Portfolio Segment [Member]
Financing Receivable, Impaired [Line Items]
Total Loans and Leases		5,949,339
Commercial Real Estate Portfolio Segment [Member] | (1) - (6) Pass [Member]
Financing Receivable, Impaired [Line Items]
Total Loans and Leases		5,860,981
Commercial Real Estate Portfolio Segment [Member] | (7) Special Mention [Member]
Financing Receivable, Impaired [Line Items]
Total Loans and Leases		26,978
Commercial Real Estate Portfolio Segment [Member] | (8) Substandard [Member]
Financing Receivable, Impaired [Line Items]
Total Loans and Leases		61,380
Commercial Real Estate Portfolio Segment [Member] | (9) Doubtful [Member]
Financing Receivable, Impaired [Line Items]
Total Loans and Leases		0
Finance Leases Portfolio Segment [Member]
Financing Receivable, Impaired [Line Items]
Total Loans and Leases		537,341
Finance Leases Portfolio Segment [Member] | (1) - (6) Pass [Member]
Financing Receivable, Impaired [Line Items]
Total Loans and Leases		528,561
Finance Leases Portfolio Segment [Member] | (7) Special Mention [Member]
Financing Receivable, Impaired [Line Items]
Total Loans and Leases		808
Finance Leases Portfolio Segment [Member] | (8) Substandard [Member]
Financing Receivable, Impaired [Line Items]
Total Loans and Leases		7,972
Finance Leases Portfolio Segment [Member] | (9) Doubtful [Member]
Financing Receivable, Impaired [Line Items]
Total Loans and Leases		$ 0