Loans and Leases (Commercial, Commercial Real Estate Loans And Equipment Financing Loans Segregated By Risk Rating Exposure) (Detail) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018	Sep. 30, 2018
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	$ 19,551,646	$ 18,465,489	$ 18,321,019
Commercial Portfolio Segment [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	6,488,056	6,216,606	6,174,396
Commercial Portfolio Segment [Member] | (1) - (6) Pass [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	6,122,391	5,781,138
Commercial Portfolio Segment [Member] | (7) Special Mention [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	97,969	206,351
Commercial Portfolio Segment [Member] | (8) Substandard [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	263,833	222,405
Commercial Portfolio Segment [Member] | (9) Doubtful [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	3,863	6,712
Commercial Real Estate Portfolio Segment [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	5,398,084	4,927,145	4,771,325
Commercial Real Estate Portfolio Segment [Member] | (1) - (6) Pass [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	5,253,649	4,773,298
Commercial Real Estate Portfolio Segment [Member] | (7) Special Mention [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	81,256	75,338
Commercial Real Estate Portfolio Segment [Member] | (8) Substandard [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	63,179	78,509
Commercial Real Estate Portfolio Segment [Member] | (9) Doubtful [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	0	0
Finance Leases Portfolio Segment [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	521,828	508,397	$ 519,054
Finance Leases Portfolio Segment [Member] | (1) - (6) Pass [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	512,219	494,585
Finance Leases Portfolio Segment [Member] | (7) Special Mention [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	915	1,303
Finance Leases Portfolio Segment [Member] | (8) Substandard [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	8,694	12,509
Finance Leases Portfolio Segment [Member] | (9) Doubtful [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	$ 0	$ 0