Schedule of Gains (Losses) on Derivative Instruments (Detail) (Hedge Derivatives, Net, Cash Flow Hedging, USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Hedge Derivatives, Net | Cash Flow Hedging
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain (Loss) Recognized in AOCI on Derivatives (Effective Portion)	$ 31	$ (19)	$ 21	$ (28)
Gain (Loss) Reclassified from AOCI into Fuel Expense	(1)	(9)	(4)	(18)
Amount of Gain (Loss) Recognized in Nonoperating income (expense) (Ineffective Portion)	$ 5	$ (1)	$ 4	$ (1)