Derivative Financial Instruments - Derivative Fair Values in Consolidated Balance Sheet for Our Non-Qualifying Hedges (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Derivatives, Fair Value [Line Items]
Total Asset Derivatives Fair Value	$ (474)	$ (1,091)
Total Liability Derivatives Fair Value	1	4
Interest rate swaps [Member] \| Derivative financial assets [Member]
Derivatives, Fair Value [Line Items]
Interest rate swaps, Derivative financial assets, fair value	(458)	(1,084)
Interest rate swaps [Member] \| Derivative Related Liabilities [Member]
Derivatives, Fair Value [Line Items]
Interest rate swaps, Derivative related liabilities, fair value	1	4
Currency swaps and foreign exchange forward contracts [Member] \| Derivative financial assets [Member]
Derivatives, Fair Value [Line Items]
Currency swaps and foreign exchange forward contracts, Derivative financial assets	(16)	(7)
Currency swaps and foreign exchange forward contracts [Member] \| Derivative Related Liabilities [Member]
Derivatives, Fair Value [Line Items]
Currency swaps and foreign exchange forward contracts, Derivative related liabilities

Fair value as of the balance sheet date of derivative instrument not designated as hedging instrument and classified as an asset.

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 107

-Paragraph 10

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 4B

-Subparagraph (c)(2)

-URI http://asc.fasb.org/extlink&oid=7476318&loc=SL5624163-113959

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- Definition

Fair value as of the balance sheet date of derivative instrument not designated as hedging instrument and classified as a liability.

+ References

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- Definition

Fair value as of the balance sheet date of all foreign currency derivative assets not designated as hedging instruments.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 133

-Paragraph 17

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 4B

-Subparagraph (c)(2)

-URI http://asc.fasb.org/extlink&oid=7476318&loc=SL5624163-113959

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- Definition

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- Definition

Fair value as of the balance sheet date of all derivative assets not designated as hedging instruments.

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