Loans (Net (Charge-Offs)/Recoveries, Segregated By Class Of Loans) (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Accounts, Notes, Loans and Financing Receivable [Line Items]
Net charge-offs	$ (2,747)	$ (16,318)	$ (10,701)	$ (38,328)
Commercial And Industrial, Energy [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Net charge-offs		1	4	5
Commercial And Industrial, Other Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Net charge-offs	(4,656)	(13,602)	(9,511)	(25,154)
Commercial Real Estate, Buildings, Land And Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Net charge-offs	2,678	(1,162)	811	(8,689)
Commercial Real Estate Construction Financing Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Net charge-offs	14	(121)	36	(473)
Consumer Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Net charge-offs	(156)	(750)	(441)	(1,642)
Consumer And Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Net charge-offs	$ (627)	$ (684)	$ (1,600)	$ (2,375)