Financial Instruments - Schedule of Investments Classified as Investments-Trading (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Schedule of Trading Securities and Other Trading Assets [Line Items]
Investments-trading	$ 176,139	$ 124,546
U.S. government agency MBS and CMOs [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Investments-trading	34,592	7,563
U.S. government agency debt securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Investments-trading	21,066	14,600
RMBS [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Investments-trading	583	7,108
CMBS [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Investments-trading	12	1,587
U.S. Treasury securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Investments-trading	147	8,524
Interests in securitizations [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Investments-trading	352	608
SBA loans [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Investments-trading	15,705	9,049
Corporate bonds and redeemable preferred stock [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Investments-trading	56,022	65,445
Foreign government bonds [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Investments-trading	448	67
Municipal bonds [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Investments-trading	37,745	9,225
Certificates of deposit [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Investments-trading	8,934	710
Equity securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Investments-trading	$ 533	$ 60

The total of financial instruments that are bought and held principally for the purpose of selling them in the near term (thus held for only a short period of time) or for debt and equity securities formerly categorized as available-for-sale or held-to-maturity which the entity held as of the date it opted to account for such securities at fair value. An enterprise may also categorize such a security as trading without the intent to sell it in the near term assuming the decision to categorize the security as trading occurred at acquisition.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.4)

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

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 45

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6871852&loc=d3e26626-111562

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 45

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6871852&loc=d3e26610-111562

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 13

-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.

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Trading Securities

-URI http://asc.fasb.org/extlink&oid=6526789

Reference 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 12

-Subparagraph a

-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.

Reference 7: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 159

-Paragraph 29

-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.

Reference 8: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Implementation Guide (Q and A)

-Number FAS115

-Paragraph 35

-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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