DERIVATIVE INSTRUMENTS - FAIR VALUE OF HEDGE POSITIONS (DETAILS) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Derivative [Line Items]
Net cash received (paid) to for new positions and settlements	$ (19)	$ 16	$ (16)
B737-800 [Member]
Derivative [Line Items]
Capital Leased Assets, Number of B737-800 Aircraft	6
Not Designated as Hedging Instrument [Member] | Fuel hedge contracts [Member]
Derivative [Line Items]
Fuel hedge contracts outstanding (in gallons)	454,000,000