Supplemental Financial Information - Accrued Liabilities (Details) - USD ($) $ in Millions		Jun. 30, 2017	Dec. 31, 2016
Accrued Liabilities, Current [Abstract]
ProfitSharing and savings plans		$ 325	$ 645
Aircraft and other lease related obligations		49	55
Vacation pay		339	355
Accrued union bonuses		69	188
Health		96	96
Workers compensation		175	183
Property and income taxes		134	68
Other		205	237
Accrued liabilities		1,561	1,985
Fuel derivatives | Accrued Liabilities
Accrued Liabilities, Current [Abstract]
Derivative contracts	[1]	$ 169	$ 158

[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.