Derivatives (Narrative) (Details) (USD $) In Millions, unless otherwise specified	6 Months Ended		3 Months Ended		6 Months Ended
	Jun. 30, 2014	Dec. 31, 2013	Jun. 30, 2014 Fuel Contracts [Member]	Jun. 30, 2013 Fuel Contracts [Member]	Jun. 30, 2014 Fuel Contracts [Member]	Jun. 30, 2013 Fuel Contracts [Member]
Derivative [Line Items]
Derivative Instruments, Gain (Loss) Recognized in Income, Net			$ 97	$ (78)	$ 175	$ (1)
Cash Flow Hedge Gain to be Reclassified within Twelve Months	107
Derivative, Collateral, Obligation to Return Cash	$ (5)	$ (65)