Acquisitions - Reconciliation of Goodwill and Other Indefinite Lived Intangibles (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2011	Dec. 31, 2012
Business Acquisition Actual Revenue And Pre Tax Income Loss [Line Items]
Goodwill balance at December 31, 2010	$ 61,631	$ 628,877
Deferred tax purchase accounting adjustment made during 2012		(22,285)
Goodwill from Whitney acquisition at acquisition date	513,917
Purchase accounting fair value adjustments subsequent to acquisition date made during the fourth quarter of 2011	75,614
Goodwill ending balance	$ 651,162	$ 628,877

Carrying amount as of the balance sheet date, which is the cumulative amount paid and (if applicable) the fair value of any noncontrolling interest in the acquiree, adjusted for any amortization recognized prior to the adoption of any changes in generally accepted accounting principles (as applicable) and for any impairment charges, in excess of the fair value of net assets acquired in one or more business combination transactions.

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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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