Derivative Financial Instruments - Location of Derivative Fair Values in Consolidated Balance Sheet (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Derivative Instruments, Gain (Loss) [Line Items]
Total Asset fair value hedges	$ 0	$ 7
Total liability fair value hedges	0	0
Derivative financial assets [Member] \| Interest rate swaps [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Interest rate swaps, Derivative financial assets at fair value	0	7
Derivative financial assets [Member] \| Currency swaps [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Currency swaps, Derivative finacial assets at fair value	0	0
Derivative Related Liabilities [Member] \| Interest rate swaps [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Interest rate swaps, Derivative related liabilities at fair value	0	0
Derivative Related Liabilities [Member] \| Currency swaps [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Currency swaps, Derivative related liabilities at fair value	$ 0	$ 0

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Fair value of all derivative assets designated as fair value hedging instruments.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 4B

-Subparagraph (c)(1)

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

Reference 2: 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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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.

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- Definition

Fair value of all derivative liabilities designated as fair value hedging instruments.

+ References

+ Details

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- Definition

Fair value as of the balance sheet date of all derivative assets designated as foreign currency fair value hedging instruments.

+ References

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- Definition

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+ References

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Fair value as of the balance sheet date of all derivative assets designated as interest rate fair value hedging instruments.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 4B

-Subparagraph (c)(1)

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

Reference 2: 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.

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Fair value as of the balance sheet date of all derivative liabilities designated as interest rate fair value hedging instruments.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 4B

-Subparagraph (c)(1)

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

Reference 2: 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.

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