Financial Instruments And Risk Management (Effect Of Cash Flow Hedges On Financial Statements) (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013		Dec. 31, 2012
Derivatives, Fair Value [Line Items]
Fuel derivative contracts, Fair Value	$ 66	[1]	$ 65
Collateral Already Posted, Aggregate Fair Value	0		0
Fuel Derivative Contracts (asset) [Member]
Derivatives, Fair Value [Line Items]
Fuel derivative contracts, Fair Value	66		65
Accrued Liabilites [Member]
Derivatives, Fair Value [Line Items]
Fuel derivative liability in accrued liabilities, Fair Value	$ 0		$ 0

[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.