Acquisitions - Change in Liability (Detail) (Whitney Holding Corporation [Member], USD $)	12 Months Ended
Dec. 31, 2012	Dec. 31, 2011
Whitney Holding Corporation [Member]
Business Acquisition, Contingent Consideration [Line Items]
Balance, January 1	$ 23,183
Adjustments	1,127	57,964
Cash Payments	(16,145)	(34,781)
Balance, December 31	$ 8,165	$ 23,183

Amount of potential cash payments that could result from the contingent consideration arrangement.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 141

-Paragraph 51

-Subparagraph f

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant