Financial Instruments - Schedule of Interest Rate Swap Agreements Designated as Cash Flow Hedges (Detail) (Pay-fixed interest rate swaps [Member], USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2012
Maturity Date, 2014 [Member]
Derivative Instruments [Line Items]
Fair Value	$ (10)
Pay-fixed interest rate swaps	Dec. 31, 2014
Notional Amount	500
Maturity Date, 2016 [Member]
Derivative Instruments [Line Items]
Fair Value	(346)
Pay-fixed interest rate swaps	Dec. 31, 2016
Notional Amount	3,000
Maturity Date, 2017 [Member]
Derivative Instruments [Line Items]
Fair Value	(73)
Pay-fixed interest rate swaps	Dec. 31, 2017
Notional Amount	$ 1,000

Aggregate notional amount of all interest rate derivatives designated as hedging instruments in cash flow hedges. Notional amount refers to the monetary amount specified in the interest rate derivative contract.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 1A

-Subparagraph (d)

-URI http://asc.fasb.org/extlink&oid=7476318&loc=SL5579245-113959

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

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Notional Amount

-URI http://asc.fasb.org/extlink&oid=6519104

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 1B

-URI http://asc.fasb.org/extlink&oid=7476318&loc=SL5580258-113959

Name:	us-gaap_NotionalAmountOfInterestRateCashFlowHedgeDerivatives
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant