Supplemental Financial Information - Other Assets (Details) - USD ($) $ in Millions		Jun. 30, 2017	Dec. 31, 2016
Other Assets [Abstract]
Asset derivative contracts, net		$ 92	$ 120
Intangible assets		419	426
Capital lease receivable		83	90
Non-current prepaid maintenance		186	6
Other		149	132
Other assets		929	774
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]	91	120
Other Assets | Interest rate derivatives
Other Assets [Abstract]
Asset derivative contracts, net	[1]	$ 1	$ 0

[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.