Investment Securities - Additional Information (Detail) (USD $) In Billions, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Investments Debt And Equity Securities [Abstract]
Weighted-average maturity of the available-for-sale investment securities (in years)	5 years 6 months	4 years 1 month 6 days
Weighted-average yields of available-for-sale investment securities	2.70%	2.93%
Weighted-average maturity of the held-to-maturity investment securities (in years)	4 years 2 months 12 days	3 years 3 months 18 days
Weighted-average yields of held-to-maturity investment securities	1.97%	1.94%
Fair value of securities pledged	$ 15.5	$ 20.1
Fair value of securities pledged as collateral where counterparty has right to repledge or resell	$ 2.0	$ 3.5

The fair value as of the balance sheet date of financial instruments and other positions owned by the entity and pledged to counterparties as collateral, including: (1) mortgages, mortgage-backed and asset backed securities; (2) US government and agency obligations; (3) state and municipal government obligations; (4) other sovereign government debt; (5) corporate obligations; (6) corporate equities; (7) principal investments; (8) derivative contracts; and (9) physical commodities.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 860

-SubTopic 30

-Section 50

-Paragraph 1A

-Subparagraph (c)(2)

-URI http://asc.fasb.org/extlink&oid=7523297&loc=SL6224234-111729

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 860

-SubTopic 30

-Section 45

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6467456&loc=d3e113888-111728

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