Fair Value Disclosures (Summary Of Assets And Liabilities Measured At Fair Value On Recurring Basis) (Details) (USD $) In Millions	9 Months Ended
	Sep. 30, 2011
Fair Value of Assets and Liabilities Measured on Recurring Basis, Gross	$ 3,992	[1],[2]
Fair Value of Assets and Liabilities Measured on Recurring Basis	4,572	[1]
Significant transfers between Level 1 and Level 2	0
Changes in valuation techniques or inputs occurred	no
Money Market Funds [Member]
Fair Value of Assets and Liabilities Measured on Recurring Basis, Gross	1,071	[1],[2]
Money Market Funds [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value of Assets and Liabilities Measured on Recurring Basis, Gross	1,071	[1],[2]
Government Agency Investments [Member]
Fair Value of Assets and Liabilities Measured on Recurring Basis, Gross	529	[1],[2]
Short-term investments mature in one year or less	529
Government Agency Investments [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value of Assets and Liabilities Measured on Recurring Basis, Gross	529	[1],[2]
Repurchase Investments [Member]
Fair Value of Assets and Liabilities Measured on Recurring Basis, Gross	811	[1],[2]
Repurchase Investments [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value of Assets and Liabilities Measured on Recurring Basis, Gross	811	[1],[2]
Corporate Obligations [Member]
Fair Value of Assets and Liabilities Measured on Recurring Basis, Gross	806	[1],[2]
Short-term investments mature in one year or less	702
Corporate Obligations [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value of Assets and Liabilities Measured on Recurring Basis, Gross	806	[1],[2]
Bank Notes or Certificates of Deposit or Time Deposits [Member]
Fair Value of Assets and Liabilities Measured on Recurring Basis, Gross	775	[1],[2]
Short-term investments mature in one year or less	569
Bank Notes or Certificates of Deposit or Time Deposits [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value of Assets and Liabilities Measured on Recurring Basis, Gross	775	[1],[2]
Restricted Cash and Short Term Investments [Member]
Fair Value of Assets and Liabilities Measured on Recurring Basis, Gross	474	[1]
Restricted Cash and Short Term Investments [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value of Assets and Liabilities Measured on Recurring Basis, Gross	474	[1]
Fuel Derivative Contracts [Member]
Fair Value of Assets and Liabilities Measured on Recurring Basis, Gross	106	[1]
Fuel Derivative Contracts [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value of Assets and Liabilities Measured on Recurring Basis, Gross	106	[1]
Fair Value, Inputs, Level 1 [Member]
Fair Value of Assets and Liabilities Measured on Recurring Basis, Gross	1,071	[1],[2]
Fair Value of Assets and Liabilities Measured on Recurring Basis	1,545	[1]
Fair Value, Inputs, Level 2 [Member]
Fair Value of Assets and Liabilities Measured on Recurring Basis, Gross	2,921	[1],[2]
Fair Value of Assets and Liabilities Measured on Recurring Basis	$ 3,027	[1]

[1] Unrealized gains or losses on short-term investments, restricted cash and short-term investments and derivatives qualifying for hedge accounting are recorded in Accumulated other comprehensive income (loss) (OCI) at each measurement date.

[2] The majority of the Company's short-term investments mature in one year or less except for $569 million of Bank notes/Certificates of deposit/Time deposits, $529 million of U.S. Government agency investments and $702 million of Corporate obligations which have maturity dates exceeding one year.