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This element represents the aggregate of the assets reported on the balance sheet at period end measured at fair value on a nonrecurring basis by the entity. This element is intended to be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements.

+ References

No definition available.

+ Details

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

- Definition

Interest rate used to find the present value of an amount to be paid or received in the future as an input to measure fair value. For example, but not limited to, weighted average cost of capital (WACC), cost of capital, cost of equity and cost of debt.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 820

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (bbb)

-URI http://asc.fasb.org/extlink&oid=7578670&loc=d3e19207-110258

+ Details

Name:	us-gaap_FairValueInputsDiscountRate
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Description of significant assumptions used by management to measure fair value.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 825

-SubTopic 10

-Section 50

-Paragraph 10

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=7491637&loc=d3e13433-108611

+ Details

Name:	us-gaap_FairValueMeasurementsSignificantAssumptions
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Description of the inputs and valuation technique(s) used to measure fair value.

+ References

+ Details

Name:	us-gaap_FairValueMeasurementsValuationTechniques
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Fair Value Measurements - Quantitative Information about Non Recurring Fair Value Measurement of Assets and Liabilities (Detail) (USD $) In Millions, unless otherwise specified							9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012 Residential Mortgage [Member]	Sep. 30, 2011 Residential Mortgage [Member]	Sep. 30, 2012 Impaired loans [Member]	Sep. 30, 2011 Impaired loans [Member]	Sep. 30, 2012 Level 3 [Member] Residential Mortgage [Member]	Sep. 30, 2012 Level 3 [Member] Residential Mortgage [Member] Third Party Appraisal [Member]	Sep. 30, 2012 Level 3 [Member] Residential Mortgage [Member] Minimum [Member]	Sep. 30, 2012 Level 3 [Member] Residential Mortgage [Member] Maximum [Member]	Sep. 30, 2012 Level 3 [Member] Impaired loans [Member]	Sep. 30, 2012 Level 3 [Member] Impaired loans [Member] Third Party Appraisal On Impaired Loans [Member]	Sep. 30, 2012 Level 3 [Member] Impaired loans [Member] Minimum [Member]	Sep. 30, 2012 Level 3 [Member] Impaired loans [Member] Maximum [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair Value	$ 519	$ 779	$ 108	$ 233	$ 309	$ 415	$ 108				$ 309
Significant Unobservable Inputs							Loss severity rates				Loss severity rates
Range of Inputs										90.00%			2.00%	61.00%
Valuation Technique(s)								Valuation of third party appraisal on underlying collateral				Valuation by third party appraisal on underlying collateral