Derivative Financial Instruments - Gain or Loss Recorded on Our Cash Flow Hedging Relationships (Detail) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Derivatives, Fair Value [Line Items]
Gain (Loss) Recognized in AOCI on Derivative (Effective Portion)	$ 7	$ 17	$ 33	$ 45
Gain (Loss) Reclassed From AOCI into Income (Effective Portion)	(3)	(2)	(9)	(8)
Interest rate swaps [Member]
Derivatives, Fair Value [Line Items]
Gain (Loss) Recognized in AOCI on Derivative (Effective Portion), Interest Rate Swaps	10	14	30	35
Currency swaps [Member]
Derivatives, Fair Value [Line Items]
Gain (Loss) Recognized in AOCI on Derivative (Effective Portion), Currency Swaps	(3)	3	3	10
Interest Expense [Member] \| Interest rate swaps [Member]
Derivatives, Fair Value [Line Items]
Gain (Loss) Reclassed from AOCI into Income (Effective Portion), Interest Rate Swaps	0	0	0	1
Interest Expense [Member] \| Currency swaps [Member]
Derivatives, Fair Value [Line Items]
Gain (Loss) Reclassed from AOCI into Income (Effective Portion), Currency swaps	(3)	(2)	(9)	(9)
Derivative related income (loss) [Member]
Derivatives, Fair Value [Line Items]
Gain (Loss) Recognized In Income on Derivative (Ineffective Portion)	5	4	12	12
Derivative related income (loss) [Member] \| Interest rate swaps [Member]
Derivatives, Fair Value [Line Items]
Gain (Loss) Recognized in Income on Derivative (Ineffective Portion), Interest Rate Swaps	0	0	0	0
Derivative related income (loss) [Member] \| Currency swaps [Member]
Derivatives, Fair Value [Line Items]
Gain (Loss) Recognized in Income on Derivative (Ineffective Portion, Currency swaps)	$ 5	$ 4	$ 12	$ 12

Unrealized Gain Loss On Cash Flow Hedges PreTax Accumulated Other Comprehensive Income Loss

No definition available.

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- Definition

The effective portion of net gain (loss) reclassified from accumulated other comprehensive income into income on derivative instruments designated and qualifying as 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 4C

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=56946850&loc=SL5624171-113959

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 4D

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=56946850&loc=SL5624177-113959

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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- Definition

The amount of net gains or losses on foreign currency cash flow hedges reclassified during the period to earnings from accumulated other comprehensive income upon the hedged transaction affecting earnings.

+ References

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- Definition

The net gain (loss) recognized in earnings during the reporting period representing the amount of the cash flow hedges' ineffectiveness.

+ References

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- Definition

The net gain (loss) during the reporting period due to ineffectiveness in foreign currency cash flow hedges. Recognized in earnings.

+ References

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- Definition

The net gain (loss) during the reporting period due to ineffectiveness in interest rate cash flow hedges. Recognized in earnings.

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- Definition

The amount of net gains or losses on interest rate cash flow hedges reclassified during the period to earnings from accumulated other comprehensive income upon the hedged transaction affecting earnings.

+ References

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- Definition

Amount of unrealized gain (loss) related to the increase or decrease in fair value of interest rate derivatives designated as cash flow hedging instruments, which was recorded in accumulated other comprehensive income to the extent that the cash flow hedge was determined to be effective.

+ References

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- Definition

Amount of unrealized gain related to the increase in fair value of foreign currency exchange rate derivatives designated as cash flow hedging instruments. Recorded in accumulated other comprehensive income to the extent that the cash flow hedge is determined to be effective.

+ References

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