Financial Derivative Instruments Narrative (Details) (USD $)	3 Months Ended				3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014 Fuel derivatives	Dec. 31, 2013 Fuel derivatives	Mar. 31, 2014 Cash Flow Hedging		Mar. 31, 2013 Cash Flow Hedging		Mar. 31, 2014 Cash Flow Hedging Fuel derivatives		Mar. 31, 2013 Cash Flow Hedging Fuel derivatives		Mar. 31, 2014 Cash Flow Hedging Interest rate derivatives		Mar. 31, 2013 Cash Flow Hedging Interest rate derivatives		Mar. 31, 2014 Remainder of 2014	Mar. 31, 2014 Other Noncurrent Liabilities Interest rate derivatives	Dec. 31, 2013 Other Noncurrent Liabilities Interest rate derivatives
Derivative [Line Items]
Total Collateral Already Posted Aggregate Fair Value			$ 0	$ 0
Total Letters of Credit or Aircraft Collateral Already Posted Aggregate Fair Value			0
Percent of fuel consumption hedged	54.00%																34.00%
Cash collateral deposits provided to counterparty - noncurrent																		32,000,000	32,000,000
Premiums paid for fuel derivative contracts	17,000,000	5,000,000
Current Unrealized Net Gains (Losses) in OCI	(1,000,000)
Cumulative ineffectiveness recognized for unsettled hedges	95,000,000
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net					(4,000,000)	[1]	(31,000,000)	[1]	0	[1],[2]	(26,000,000)	[1],[2]	(4,000,000)	[1],[2]	(5,000,000)	[1],[2]
Maximum sum of derivatives of counterparty to be included in other (less than $20 million)	$ 20,000,000
Cash collateral provided as a percentage of derivative contract value (in hundredths)	100.00%

[1] Amounts related to fuel derivative contracts and interest rate derivatives are included in Fuel and oil and Interest expense, respectively.

[2] Net of tax