Loans and Leases and the Allowance for Credit Losses - Changes in Allowance for Credit Losses (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	$ 916,676	$ 925,860
Provision for credit losses	32,000	38,000
Net charge-offs
Charge-offs	(47,439)	(48,948)
Recoveries	15,531	12,205
Net charge-offs	(31,908)	(36,743)
Ending balance	916,768	927,117
Commercial, Financial, Leasing, etc. [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	273,383	246,759
Provision for credit losses	12,598	17,880
Net charge-offs
Charge-offs	(14,809)	(9,544)
Recoveries	5,663	2,756
Net charge-offs	(9,146)	(6,788)
Ending balance	276,835	257,851
Real Estate Commercial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	324,978	337,101
Provision for credit losses	116	(312)
Net charge-offs
Charge-offs	(3,486)	(9,588)
Recoveries	3,197	815
Net charge-offs	(289)	(8,773)
Ending balance	324,805	328,016
Residential Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	78,656	88,807
Provision for credit losses	4,228	5,036
Net charge-offs
Charge-offs	(7,453)	(8,171)
Recoveries	1,631	4,450
Net charge-offs	(5,822)	(3,721)
Ending balance	77,062	90,122
Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	164,644	179,418
Provision for credit losses	14,141	14,836
Net charge-offs
Charge-offs	(21,691)	(21,645)
Recoveries	5,040	4,184
Net charge-offs	(16,651)	(17,461)
Ending balance	162,134	176,793
Unallocated [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	75,015	73,775
Provision for credit losses	917	560
Net charge-offs
Charge-offs
Recoveries
Net charge-offs
Ending balance	$ 75,932	$ 74,335