Investments And Fair Value Measurements (Assets And Liabilities Measured At Fair Value On A Recurring Basis) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets and liabilities measured on recurring basis, gross	$ 3,718	[1],[2]
Fair value of assets and liabilities measured on recurring basis	4,551
Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets and liabilities measured on recurring basis, gross	1,278	[1],[2]
Fair value of assets and liabilities measured on recurring basis	2,016
Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets and liabilities measured on recurring basis, gross	2,440	[1],[2]
Fair value of assets and liabilities measured on recurring basis	2,535
Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets and liabilities measured on recurring basis, gross		[1],[2]
Fair value of assets and liabilities measured on recurring basis
Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets and liabilities measured on recurring basis, gross	1,278	[1],[2]
Money Market Funds [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets and liabilities measured on recurring basis, gross	1,278	[1],[2]
Money Market Funds [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets and liabilities measured on recurring basis, gross		[1],[2]
Government Agency Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets and liabilities measured on recurring basis, gross	502	[1],[2]
Exception To Short-term investments mature in one year or less	502
Government Agency Investments [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets and liabilities measured on recurring basis, gross	502	[1],[2]
Government Agency Investments [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets and liabilities measured on recurring basis, gross		[1],[2]
Repurchase Agreements [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets and liabilities measured on recurring basis, gross	128	[1],[2]
Repurchase Agreements [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets and liabilities measured on recurring basis, gross	128	[1],[2]
Repurchase Agreements [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets and liabilities measured on recurring basis, gross		[1],[2]
Corporate Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets and liabilities measured on recurring basis, gross	1,102	[1],[2]
Exception To Short-term investments mature in one year or less	225
Corporate Obligations [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets and liabilities measured on recurring basis, gross	1,102	[1],[2]
Corporate Obligations [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets and liabilities measured on recurring basis, gross		[1],[2]
Bank Notes/Certificates Of Deposit/Time Deposits [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets and liabilities measured on recurring basis, gross	708	[1],[2]
Exception To Short-term investments mature in one year or less	87
Bank Notes/Certificates Of Deposit/Time Deposits [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets and liabilities measured on recurring basis, gross	708	[1],[2]
Bank Notes/Certificates Of Deposit/Time Deposits [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets and liabilities measured on recurring basis, gross		[1],[2]
Restricted Cash And Short-Term Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets and liabilities measured on recurring basis	738	[1]
Restricted Cash And Short-Term Investments [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets and liabilities measured on recurring basis	738	[1]
Restricted Cash And Short-Term Investments [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets and liabilities measured on recurring basis		[1]
Fuel Derivative Contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets and liabilities measured on recurring basis	95	[1]
Fuel Derivative Contracts [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets and liabilities measured on recurring basis	95	[1]
Fuel Derivative Contracts [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets and liabilities measured on recurring basis		[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) at each measurement date.

[2] The Company's short-term investments mature in one year or less except for $87 million of Bank notes/Certificates of deposit/Time deposits, $502 million of U.S. Government agency investments and $225 million of Corporate obligations which have maturity dates exceeding one year.