Fair Value Disclosures (Summary Of Assets And Liabilities Measured At Fair Value On Recurring Basis) (Details) (USD $) In Millions	6 Months Ended
	Jun. 30, 2011
Fair Value of Assets and Liabilities Measured on Recurring Basis, Gross	$ 4,858
Fair Value of Assets and Liabilities Measured on Recurring Basis	5,677
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	207
Money Market Funds [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value of Assets and Liabilities Measured on Recurring Basis, Gross	207
Government Agency Investments [Member]
Fair Value of Assets and Liabilities Measured on Recurring Basis, Gross	554
Short-term investments mature in one year or less	554
Government Agency Investments [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value of Assets and Liabilities Measured on Recurring Basis, Gross	554
Repurchase Investments [Member]
Fair Value of Assets and Liabilities Measured on Recurring Basis, Gross	1,621
Repurchase Investments [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value of Assets and Liabilities Measured on Recurring Basis, Gross	1,621
Corporate Obligations [Member]
Fair Value of Assets and Liabilities Measured on Recurring Basis, Gross	799
Short-term investments mature in one year or less	427
Corporate Obligations [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value of Assets and Liabilities Measured on Recurring Basis, Gross	799
Bank Notes or Certificates of Deposit or Time Deposits [Member]
Fair Value of Assets and Liabilities Measured on Recurring Basis, Gross	1,677
Short-term investments mature in one year or less	721
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	1,677
Restricted Cash and Short Term Investments [Member]
Fair Value of Assets and Liabilities Measured on Recurring Basis, Gross	457
Restricted Cash and Short Term Investments [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value of Assets and Liabilities Measured on Recurring Basis, Gross	457
Fuel Derivative Contracts [Member]
Fair Value of Assets and Liabilities Measured on Recurring Basis, Gross	362
Fuel Derivative Contracts [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value of Assets and Liabilities Measured on Recurring Basis, Gross	362
Fair Value, Inputs, Level 1 [Member]
Fair Value of Assets and Liabilities Measured on Recurring Basis, Gross	207
Fair Value of Assets and Liabilities Measured on Recurring Basis	664
Fair Value, Inputs, Level 2 [Member]
Fair Value of Assets and Liabilities Measured on Recurring Basis, Gross	4,651
Fair Value of Assets and Liabilities Measured on Recurring Basis	$ 5,013