DERIVATIVE INSTRUMENTS - FAIR VALUE OF HEDGE POSITIONS (Details) gallons in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015 USD ($) gallons aircraft	Jun. 30, 2014 USD ($)	Jun. 30, 2015 USD ($) gallons aircraft	Jun. 30, 2014 USD ($)	Dec. 31, 2014 USD ($)
Derivative [Line Items]
Net cash received (paid) to for new positions and settlements	$ (4)	$ 1	$ (8)	$ (6)
Posted collateral	$ 1		$ 1		$ 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