Fair Value Assets Measured on Nonrecurring Basis (Detail) (Airport Slots, USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Airport Slots
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	$ 102	$ 8
Loss	$ 30	$ 4

This element represents the aggregate of the assets reported on the balance sheet at period end measured at fair value on a nonrecurring basis by the entity. This element is intended to be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements.

No definition available.

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