Financial Instruments (Narrative) (Detail) gal in Millions, $ in Millions	3 Months Ended
Mar. 31, 2016 USD ($) gal	Mar. 31, 2015 USD ($)
Schedule of Cost-method Investments [Line Items]
Interest Rate Cash Flow Hedge Gain (Loss) to be Reclassified During Next 12 Months, Net	$ 7
Derivative Instruments, Gain (Loss) Recognized in Income, Net	(29)	$ 69
Interest Rate Caps [Member]
Schedule of Cost-method Investments [Line Items]
Absolute notional values of derivative instruments	8,674
Interest Rate Caps [Member] \| Interest Rate Caps Purchased [Member]
Schedule of Cost-method Investments [Line Items]
Absolute notional values of derivative instruments	1,800
Interest Rate Caps [Member] \| Interest Rate Caps Purchased [Member] \| Subsidiary Issuers [Member]
Schedule of Cost-method Investments [Line Items]
Absolute notional values of derivative instruments	5,100
Interest Rate Caps [Member] \| Interest Rate Caps Sold [Member]
Schedule of Cost-method Investments [Line Items]
Absolute notional values of derivative instruments	6,900
Interest Rate Swaps [Member]
Schedule of Cost-method Investments [Line Items]
Absolute notional values of derivative instruments	$ 1,850
Commodity Contracts [Member]
Schedule of Cost-method Investments [Line Items]
Units Of Gasoline \| gal	14
Currency Swap [Member]
Schedule of Cost-method Investments [Line Items]
Absolute notional values of derivative instruments	$ 1,054
Not Designated As Hedging Instruments [Member] \| Commodity Contracts [Member]
Schedule of Cost-method Investments [Line Items]
Derivative Instruments, Gain (Loss) Recognized in Income, Net	(2)	0
Interest Expense [Member]
Schedule of Cost-method Investments [Line Items]
Derivative Instruments, Gain (Loss) Recognized in Income, Net	9	21
Operating Expense [Member]
Schedule of Cost-method Investments [Line Items]
Derivative Instruments, Gain (Loss) Recognized in Income, Net	$ 19	$ 14

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- Definition

Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Article 12
-Section 13
-Sentence Column B

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- Definition

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+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4A
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=56946850&loc=SL5618551-113959

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4C
-Subparagraph (a),(c),(d),(e)
-URI http://asc.fasb.org/extlink&oid=56946850&loc=SL5624171-113959

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- Definition

The estimated net amount of unrealized gains or losses on interest rate cash flow hedges as of the balance sheet date expected to be reclassified to earnings within the next twelve months.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 30
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=35736893&loc=d3e80748-113994

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No definition available.

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