Financial Instruments And Fair Value Measurements (Activity For "Level Three" Financial Assets And Financial Liabilities) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012		Mar. 31, 2011
Auction Rate Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at January 1	$ 113	[1]	$ 119	[1]
Reported in earnings - unrealized	(1)	[1]
Reported in other comprehensive income			1	[1]
Balance at March 31	112	[1]	120	[1]
EETC [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at January 1	60	[1]	66	[1]
Settlements	(2)	[1]	(2)	[1]
Reported in other comprehensive income	4	[1]	(1)	[1]
Balance at March 31	$ 62	[1]	$ 63	[1]

[1] For 2012 and 2011, United's only Level 3 recurring measurements are the above EETCs.