Deposits - Additional Information About Corporation's Deposits (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2012
Deposits from the Certificate of Deposit Account Registry Service (CDARS) deposits	$ 901	$ 2,723	$ 25,541
Deposits from foreign sources (primarily Mexico)	$ 767,702	$ 799,504	$ 830,685

The aggregate of all foreign interest-bearing and noninterest-bearing deposit liabilities.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 235

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-05(a))

-URI http://asc.fasb.org/extlink&oid=6882215&loc=d3e537907-122884

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.12(a))

-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 12

-Subparagraph a

-Article 9

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