Loans and Leases (Commercial, Commercial Real Estate Loans And Equipment Financing Loans Segregated By Risk Rating Exposure) (Detail) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018	Jun. 30, 2018
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	$ 19,269,883	$ 18,465,489	$ 18,025,996
Commercial Portfolio Segment [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	6,519,953	6,216,606	5,981,556
Commercial Portfolio Segment [Member] | (1) - (6) Pass [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	6,124,187	5,781,138
Commercial Portfolio Segment [Member] | (7) Special Mention [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	168,290	206,351
Commercial Portfolio Segment [Member] | (8) Substandard [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	220,758	222,405
Commercial Portfolio Segment [Member] | (9) Doubtful [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	6,718	6,712
Commercial Real Estate Portfolio Segment [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	5,224,382	4,927,145	4,580,200
Commercial Real Estate Portfolio Segment [Member] | (1) - (6) Pass [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	5,047,238	4,773,298
Commercial Real Estate Portfolio Segment [Member] | (7) Special Mention [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	95,528	75,338
Commercial Real Estate Portfolio Segment [Member] | (8) Substandard [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	81,616	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	505,553	508,397	$ 522,965
Finance Leases Portfolio Segment [Member] | (1) - (6) Pass [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	495,381	494,585
Finance Leases Portfolio Segment [Member] | (7) Special Mention [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	2,560	1,303
Finance Leases Portfolio Segment [Member] | (8) Substandard [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	7,612	12,509
Finance Leases Portfolio Segment [Member] | (9) Doubtful [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	$ 0	$ 0