Supplemental Financial Information - Other Assets (Details) - USD ($) $ in Millions		Mar. 31, 2016	Dec. 31, 2015
Other Assets [Abstract]
Intangible assets		$ 460	$ 464
Non-current investments		41	40
Other		232	213
Other assets		733	717
Accrued Liabilities | Fuel derivatives
Other Assets [Abstract]
Asset derivative contracts, net	[1]	0	0
Other Assets | Fuel derivatives
Other Assets [Abstract]
Asset derivative contracts, net	[1]	15	7
Other Assets | Interest rate derivatives
Other Assets [Abstract]
Asset derivative contracts, net	[1]	$ 16	$ 2

[1] The net amounts of derivative assets and liabilities are reconciled to the individual line item amounts presented in the unaudited Condensed Consolidated Balance Sheet in Note 5.