Loans and Leases (Investments in TDRs, Segregated by Risk Rating Exposure) (Detail) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total recorded investment of TDRs	$ 245,294	$ 237,438
Commercial Portfolio Segment [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total recorded investment of TDRs	124,370	112,152
Commercial Portfolio Segment [Member] | (1) - (6) Pass [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total recorded investment of TDRs	12,591	3,952
Commercial Portfolio Segment [Member] | (7) Special Mention [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total recorded investment of TDRs	0	63
Commercial Portfolio Segment [Member] | (8) Substandard [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total recorded investment of TDRs	111,613	104,277
Commercial Portfolio Segment [Member] | (9) Doubtful [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total recorded investment of TDRs	$ 166	$ 3,860