Fair Value Measurements - Change in Balance Sheet Carrying Value Associated with Level 3 Financial Instruments Carried at Fair Value on Recurring Basis (Detail) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance, beginning of period	$ (845)	$ (751)	$ (949)	$ (216)
Total gains/(losses) (realized and unrealized):
Included in earnings	58	48	123	(487)
Included in other comprehensive income	0	0	0	0
Settlements	24	6	63	6
Transfers in and/or out of level 3	0	0	0	0
Balance, end of period	(763)	(697)	(763)	(697)
Change in unrealized gains/(losses) relating to instruments still held at the reporting date	82	48	187	(485)
Interest Rate Swaps [Member]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance, beginning of period	(37)	(82)	(44)	(88)
Total gains/(losses) (realized and unrealized):
Included in earnings	(2)	40	4	45
Included in other comprehensive income	0	0	0	0
Settlements		3	1	4
Transfers in and/or out of level 3	0	0	0	0
Balance, end of period	(39)	(39)	(39)	(39)
Change in unrealized gains/(losses) relating to instruments still held at the reporting date	(2)	37	6	42
Cross-Currency Interest Rate Swaps [Member]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance, beginning of period	(801)	(654)	(903)	(117)
Total gains/(losses) (realized and unrealized):
Included in earnings	64	(5)	129	(538)
Included in other comprehensive income	0	0	0	0
Settlements	23	3	60	(1)
Transfers in and/or out of level 3	0	0	0	0
Balance, end of period	(714)	(656)	(714)	(656)
Change in unrealized gains/(losses) relating to instruments still held at the reporting date	87	(2)	189	(536)
Other [Member]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance, beginning of period	(7)	(15)	(2)	(11)
Total gains/(losses) (realized and unrealized):
Included in earnings	(4)	13	(10)	6
Included in other comprehensive income	0	0	0	0
Settlements	1		2	3
Transfers in and/or out of level 3	0	0	0	0
Balance, end of period	(10)	(2)	(10)	(2)
Change in unrealized gains/(losses) relating to instruments still held at the reporting date	$ (3)	$ 13	$ (8)	$ 9

Change in unrealized gains/(losses) relating to instruments still held at the reporting date.

No definition available.

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- Definition

Gains losses realized and unrealized.

+ References

No definition available.

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- Definition

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

Amount of gain (loss) recognized in the income statement of financial instrument classified as a derivative asset (liability) after deduction of derivative liability (asset), measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ 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 (c)(1)
-URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
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-Section 50
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-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19279-110258

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- Definition

Amount of gain (loss) recognized in other comprehensive income (loss) of financial instrument classified as a derivative asset (liability) after deduction of derivative liability (asset), measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ 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 (c)(1a)
-URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258

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- Definition

Amount of settlements of financial instrument classified as a derivative asset (liability) after deduction of derivative liability, measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ 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 (c)(2)
-URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258

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-Publisher FASB
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-URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19279-110258

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- Definition

Amount of transfers of financial instrument classified as a derivative asset (liability) after deduction of derivative liability (asset) into (out of) level 3 of the fair value hierarchy.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19279-110258

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- Definition

Fair value of financial instrument classified as derivative asset (liability) after deduction of derivative liability (asset), measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ 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 (a)
-URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258

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-Publisher FASB
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-URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19279-110258

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