Assets Acquired In FDIC-Assisted Acquisitions - Changes in FDIC Shared Loss Receivable (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended	12 Months Ended
Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012
Banking And Thrift [Abstract]
Beginning balance	$ 159,724	$ 242,394	$ 242,394
Indemnification asset recorded in acquisitions		52,654	52,654
Payments received from FDIC	(6,324)	(71,169)	(128,730)
Effect of change in expected cash flows on covered assets	7,579	(3,863)	(6,594)
Balance, end of year	$ 160,979	$ 220,016	$ 159,724

The amount of indemnification assets (amounts to be reimbursed if and when certain assumed liabilities are paid) recognized at the acquisition date of a business combination.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 805

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (a)(1)

-URI http://asc.fasb.org/extlink&oid=6910749&loc=d3e4845-128472

Name:	us-gaap_BusinessCombinationIndemnificationAssetsAmountAsOfAcquisitionDate
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant