Loans and Leases (Summary Of The Recorded Investment Of Company's TDRs) (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total recorded investment of TDR	$ 235,427	$ 237,438
Specific reserves for TDR included in the balance of ALLL	359,431	209,096	$ 212,353	$ 199,994
Additional funds committed to borrowers in TDR status	12,895	4,856
Performing Financial Instruments [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total recorded investment of TDR	140,089	136,449
Nonperforming Financial Instruments [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total recorded investment of TDR	95,338	100,989
Troubled Debt Restructures [Member] | Nonperforming Financial Instruments [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Specific reserves for TDR included in the balance of ALLL	$ 12,728	$ 12,956