Loans and Leases (Summary Of The Recorded Investment Of Company's TDRs) (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Dec. 31, 2015	Dec. 31, 2014
Financing Receivable, Modifications [Line Items]
Total recorded investment of TDR	$ 221,404	$ 223,528
Specific reserves for TDR included in the balance of ALLL	199,994	194,320	$ 194,320	$ 174,990	$ 159,264
Additional funds committed to borrowers in TDR status	2,736	459
Performing Financial Instruments [Member]
Financing Receivable, Modifications [Line Items]
Total recorded investment of TDR	147,113	147,809
Nonperforming Financial Instruments [Member]
Financing Receivable, Modifications [Line Items]
Total recorded investment of TDR	74,291	75,719
Troubled Debt Restructures [Member]
Financing Receivable, Modifications [Line Items]
Interest receivable	100	700
Troubled Debt Restructures [Member] | Nonperforming Financial Instruments [Member]
Financing Receivable, Modifications [Line Items]
Specific reserves for TDR included in the balance of ALLL	$ 12,384	$ 14,583