Financial Instruments and Fair Value Measurements (Activity for Level Three Financial Assets and Financial Liabilities) (Details) (USD $) In Millions	3 Months Ended				6 Months Ended
	Jun. 30, 2011		Jun. 30, 2010		Jun. 30, 2011		Jun. 30, 2010
EETC [Member]
Beginning Balance	$ 63	[1]	$ 58	[1]	$ 66	[1]	$ 51	[1]
Settlements		[1]		[1]	(2)	[1]	(2)	[1]
Reported in other comprehensive income (loss)	2	[1]	3	[1]	1	[1]	12	[1]
Ending Balance	65	[1]	61	[1]	65	[1]	61	[1]
Auction Rate Securities [Member]
Beginning Balance	120	[1]			119	[1]
Settlements		[1]
Reported in earnings - unrealized	1	[1]			1	[1]
Reported in other comprehensive income (loss)		[1]			1	[1]
Ending Balance	$ 121	[1]			$ 121	[1]

[1] For 2010, amounts also represent United. For 2011, United's only Level Three recurring measurements are the above EETCs.