Investment Securities - Summary of Other Than Temporary Impairment by Investment Category (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
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Other Gains (losses)	$ 1	$ 2	$ 8	$ 3
Available-for-Sale Securities [Member]
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Losses Recorded in Earnings	(3)	(15)	(13)	(64)
Other Gains (losses)	1	2	8	3
Total Available for sale other-than-temporary impairment	(2)	(13)	(5)	(61)
Available-for-Sale Securities [Member] \| Residential Non-Agency Prime [Member]
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Losses Recorded in Earnings	(1)	(5)	(5)	(8)
Other Gains (losses)		(3)	2	(12)
Total Available for sale other-than-temporary impairment	(1)	(8)	(3)	(20)
Available-for-Sale Securities [Member] \| Residential Non-Agency Non-Prime [Member]
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Losses Recorded in Earnings	(2)	(10)	(8)	(27)
Other Gains (losses)	1	5	6	15
Total Available for sale other-than-temporary impairment	(1)	(5)	(2)	(12)
Commercial Non-Agency Mortgage-Backed Securities [Member] \| Available-for-Sale Securities [Member]
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Losses Recorded in Earnings				(1)
Other Gains (losses)				(1)
Total Available for sale other-than-temporary impairment				(2)
Perpetual preferred securities [Member] \| Available-for-Sale Securities [Member]
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Losses Recorded in Earnings				(27)
Other Gains (losses)
Total Available for sale other-than-temporary impairment				(27)
Other Asset-Backed Securities [Member] \| Available-for-Sale Securities [Member]
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Losses Recorded in Earnings				(1)
Other Gains (losses)				1
Total Available for sale other-than-temporary impairment

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The amount by which the fair value of an investment in debt and equity securities categorized as Available-for-sale is less than the amortized cost basis or carrying amount of that investment at the balance sheet date and the decline in fair value is deemed to be other than temporary, before considering whether or not such amount is recognized in earnings or other comprehensive income.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 50

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27161-111563

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- Definition

Amount before tax of other than temporary impairment (OTTI) on investment in available-for-sale debt security, recognized in other comprehensive loss.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 35

-Paragraph 35

-URI http://asc.fasb.org/extlink&oid=27723805&loc=d3e25362-111560

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 220

-SubTopic 10

-Section 45

-Paragraph 10A

-Subparagraph (g)

-URI http://asc.fasb.org/extlink&oid=28358780&loc=SL7669646-108580

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- Definition

The amount of other than temporary impairment losses on investments in debt and equity securities categorized as Available-for-sale which have been recognized in earnings during the period. Such impairment losses consist of other than temporary impairments (OTTI) on equity securities, credit losses on investments in debt securities, and when the entity intends to sell an impaired debt security or it is more likely than not that the entity will be required to sell the impaired debt security before recovery of its amortized cost basis.

+ References

+ Details

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