Commitments, Contingencies and Guarantees - Schedule of Changes in Representation and Warranty Reserves (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended	9 Months Ended
Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Commitments And Contingencies Disclosure [Abstract]
Representation and warranty repurchase reserve, beginning of period	$ 1,156	$ 1,002	$ 899	$ 943
Provision for mortgage representation and warranty losses	(4)	0	276	349
Net realized losses	(7)	(83)	(30)	(373)
Representation and warranty repurchase reserve, end of period	$ 1,145	$ 919	$ 1,145	$ 919

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Amount of loss contingency liability.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 450

-SubTopic 20

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14326-108349

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- Definition

Amount of payments made reducing loss contingency liability.

+ References

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- Definition

Amount charged against operating income increasing loss contingency liability, after adjustments to reduce previously estimated charges.

+ References

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