Securities Purchases Under Agreements to Resell (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Resale Agreement Counterparty [Line Items]
Resell agreements	$ 792	$ 1,100
Total funds sold and securities purchased under agreements to resell	$ 792	$ 1,058

Includes: (1) the amount outstanding of funds lent to other depository institutions, securities brokers, or securities dealers in the form of Federal Funds sold; for example, immediately available funds lent under agreements or contracts that mature in one business day or roll over under a continuing contract, regardless of the nature of the transaction or the collateral involved, excluding overnight lending for commercial and industrial purposes. Also include Federal Funds sold under agreements to resell on a gross basis, excluding (1) sales of term Federal Funds, (2) due bills representing purchases of securities or other assets by the reporting bank that have not yet been delivered and similar instruments, (3) resale agreements that mature in more than one business day involving assets other than securities, and (4) yield maintenance dollar repurchase agreements (Federal Funds Sold) and (2) the dollar amount outstanding of funds lent in the form of security resale agreements regardless of maturity, if the agreement requires the bank to resell the identical security purchased or a security that meets the definition of substantially the same in the case of a dollar roll. Also include purchases of participations in pools of securities, regardless of maturity (Securities Purchased Under Agreements to Re-sell).

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The carrying value of funds outstanding loaned in the form of security resale agreements if the agreement requires the purchaser to resell the identical security purchased or a security that meets the definition of "substantially the same." Also includes purchases of participations in pools of securities that are subject to a resale agreement.

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

-Publisher FASB

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

-Publisher SEC

-Name Regulation S-X (SX)

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

-Publisher FASB

-Name FASB Interpretation (FIN)

-Number 41

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

-Publisher SEC

-Name Regulation S-X (SX)

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

-Publisher FASB

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-URI http://asc.fasb.org/extlink&oid=6935251&loc=d3e9760-107771

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

-Publisher SEC

-Name Regulation S-X (SX)

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

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-Paragraph 100

-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 Accounting Standards Codification

-Topic 942

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-Section S99

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