DERIVATIVE INSTRUMENTS - FAIR VALUE OF HEDGE POSITIONS (Details) gallons in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015 USD ($) gallons aircraft	Sep. 30, 2014 USD ($)	Sep. 30, 2015 USD ($) gallons aircraft	Sep. 30, 2014 USD ($)	Dec. 31, 2014 USD ($)
Derivative [Line Items]
Net cash received (paid) to for new positions and settlements	$ (4)	$ 1	$ 12	$ 4
Posted collateral	$ 5		$ 5		$ 3
B737-800 [Member]
Derivative [Line Items]
Number of aircraft under operating lease (in Aircraft) | aircraft	6		6
Not Designated as Hedging Instrument [Member] | Fuel hedge contracts [Member]
Derivative [Line Items]
Fuel hedge contracts outstanding (in barrels) | gallons	259		259