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	6 Months Ended
Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Fair Value Net Derivative Asset Liability Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Balance, beginning of period	$ (232)	$ (678)	$ (302)	$ (593)
Total gains/(losses):
Included in earnings	112	48	175	(59)
Included in other comprehensive income	0	0	0	0
Settlements	6	13	13	35
Transfers in and/or out of level 3	0	0	0	0
Balance, end of period	(114)	(617)	(114)	(617)
Change in mark-to-market gains/(losses) relating to instruments still held at the reporting date	22	61	(74)	(27)
Interest Rate Swaps [Member]
Fair Value Net Derivative Asset Liability Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Balance, beginning of period	(7)	(12)	(8)	(17)
Total gains/(losses):
Included in earnings	1	1	2	6
Included in other comprehensive income	0	0	0	0
Settlements	0		0
Transfers in and/or out of level 3	0	0	0	0
Balance, end of period	(6)	(11)	(6)	(11)
Change in mark-to-market gains/(losses) relating to instruments still held at the reporting date	1	1	2	3
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	(225)	(666)	(294)	(575)
Total gains/(losses):
Included in earnings	111	47	173	(65)
Included in other comprehensive income	0	0	0	0
Settlements	6	13	13	34
Transfers in and/or out of level 3	0	0	0	0
Balance, end of period	(108)	(606)	(108)	(606)
Change in mark-to-market gains/(losses) relating to instruments still held at the reporting date	21	60	(76)	(31)
Other [Member]
Fair Value Net Derivative Asset Liability Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Balance, beginning of period				(1)
Total gains/(losses):
Included in earnings	0		0
Included in other comprehensive income	0	0	0	0
Settlements	0		0	1
Transfers in and/or out of level 3	0	$ 0	0	0
Balance, end of period	0		0
Change in mark-to-market gains/(losses) relating to instruments still held at the reporting date	$ 0		$ 0	$ 1

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

No definition available.

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- Definition

Fair value net derivative asset (liability) measured on recurring basis unobservable input reconciliation gains (losses).

+ References

No definition available.

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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

Amount of gain (loss) recognized in income from derivative asset (liability) after deduction of derivative liability (asset), measured at fair value on recurring basis using unobservable input (level 3).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
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- Definition

Amount of gain (loss) recognized in other comprehensive income from derivative asset (liability) after deduction of derivative liability (asset), measured at fair value on recurring basis using unobservable input (level 3).

+ References

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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

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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

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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.

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