Financial Instruments And Risk Management (Effect Of Cash Flow Hedges On Financial Statements) (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Derivatives, Fair Value [Line Items]
Cash Flow Hedge Derivative Instrument Assets at Fair Value	$ 65	$ 97
Fuel Derivative Contracts [Member]
Derivatives, Fair Value [Line Items]
Cash Flow Hedge Derivative Instrument Assets at Fair Value	65	97
Accrued Liabilities [Member]
Derivatives, Fair Value [Line Items]
Fuel derivative liability, Fair Value	$ 0	$ 2

Fair value of all liability derivatives designated as cash flow hedging instruments.

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 107

-Paragraph 10

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 4B

-Subparagraph (c)(1)

-URI http://asc.fasb.org/extlink&oid=6935481&loc=SL5624163-113959

Name:	us-gaap_CashFlowHedgeDerivativeInstrumentLiabilitiesAtFairValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant