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, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Accounts, Notes, Loans and Financing Receivable [Line Items]
Net charge-offs	$ (5,361)	$ (2,747)	$ (25,989)	$ (10,701)
Commercial and industrial, Energy [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Net charge-offs	0	0	(900)	4
Commercial and industrial, Other commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Net charge-offs	(4,296)	(4,656)	(22,806)	(9,511)
Commercial real estate, Buildings, land and other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Net charge-offs	110	2,678	81	811
Commercial real estate, Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Net charge-offs	16	14	246	36
Consumer Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Net charge-offs	(457)	(156)	(718)	(441)
Consumer and Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Net charge-offs	$ (734)	$ (627)	$ (1,892)	$ (1,600)