Financial Derivative Instruments - Fair Values of Fuel Derivatives Amounts Posted as Collateral (Details) (Fuel derivatives, USD $) In Millions, unless otherwise specified	Mar. 31, 2013
Schedule Of Fair Values Of Fuel Derivatives Amounts Posted As Collateral And Collateral Posting Thresholds [Line Items]
Fair Value of fuel derivatives	$ 200
Collateral held from (by) CP	0
Counterparty A
Schedule Of Fair Values Of Fuel Derivatives Amounts Posted As Collateral And Collateral Posting Thresholds [Line Items]
Fair Value of fuel derivatives	23
Collateral held from (by) CP	0
Counterparty B
Schedule Of Fair Values Of Fuel Derivatives Amounts Posted As Collateral And Collateral Posting Thresholds [Line Items]
Fair Value of fuel derivatives	44
Collateral held from (by) CP	0
Counterparty C
Schedule Of Fair Values Of Fuel Derivatives Amounts Posted As Collateral And Collateral Posting Thresholds [Line Items]
Fair Value of fuel derivatives	5
Collateral held from (by) CP	0
Counterparty D
Schedule Of Fair Values Of Fuel Derivatives Amounts Posted As Collateral And Collateral Posting Thresholds [Line Items]
Fair Value of fuel derivatives	16
Collateral held from (by) CP	0
Counterparty E
Schedule Of Fair Values Of Fuel Derivatives Amounts Posted As Collateral And Collateral Posting Thresholds [Line Items]
Fair Value of fuel derivatives	72
Collateral held from (by) CP	0
Counterparty F
Schedule Of Fair Values Of Fuel Derivatives Amounts Posted As Collateral And Collateral Posting Thresholds [Line Items]
Fair Value of fuel derivatives	24
Collateral held from (by) CP	0
Counterparty Other
Schedule Of Fair Values Of Fuel Derivatives Amounts Posted As Collateral And Collateral Posting Thresholds [Line Items]
Fair Value of fuel derivatives	16	[1]
Collateral held from (by) CP	0	[1]
Minimum | Counterparty A
Schedule Of Fair Values Of Fuel Derivatives Amounts Posted As Collateral And Collateral Posting Thresholds [Line Items]
Option to substitute LC for aircraft	(340)	[2]
If credit rating is investment grade, fair value of fuel derivative level at which:
Fair value of fuel derivative levels at which cash is provided to CP Threshold 1	(40)
Fair value of fuel derivative levels at which cash is provided to CP Threshold 2	(740)
Fair value of fuel derivative level at which cash is received from CP	75
Fair value of fuel derivative levels at which aircraft or cash collateral is pledged to CP	(340)	[2]
If credit rating is non-investment grade, fair value of fuel derivative level at which:
Fair value of fuel derivative levels at which cash is provided to CP Threshold 1	(40)
Fair value of fuel derivative levels at which cash is provided to CP Threshold 2	(740)
Fair value of fuel derivative level at which cash is received from CP		[3]
Fair value of fuel derivative levels at which aircraft collateral is pledged to CP	(340)
Minimum | Counterparty B
Schedule Of Fair Values Of Fuel Derivatives Amounts Posted As Collateral And Collateral Posting Thresholds [Line Items]
Option to substitute LC for aircraft	(125)	[2]
If credit rating is investment grade, fair value of fuel derivative level at which:
Fair value of fuel derivative levels at which cash is provided to CP Threshold 1	0
Fair value of fuel derivative levels at which cash is provided to CP Threshold 2	(625)
Fair value of fuel derivative level at which cash is received from CP	150
Fair value of fuel derivative levels at which aircraft or cash collateral is pledged to CP	(125)	[2]
If credit rating is non-investment grade, fair value of fuel derivative level at which:
Fair value of fuel derivative levels at which cash is provided to CP Threshold 1	0
Fair value of fuel derivative levels at which cash is provided to CP Threshold 2	(625)
Fair value of fuel derivative level at which cash is received from CP		[3]
Fair value of fuel derivative levels at which aircraft collateral is pledged to CP	(125)
Minimum | Counterparty C
Schedule Of Fair Values Of Fuel Derivatives Amounts Posted As Collateral And Collateral Posting Thresholds [Line Items]
Option to substitute LC for cash	(100)	[4]
If credit rating is investment grade, fair value of fuel derivative level at which:
Fair value of fuel derivative levels at which cash is provided to CP Threshold 1	(50)
Fair value of fuel derivative level at which cash is received from CP	175	[5]
If credit rating is non-investment grade, fair value of fuel derivative level at which:
Fair value of fuel derivative levels at which cash is provided to CP Threshold 1		[3]
Fair value of fuel derivative level at which cash is received from CP		[3]
Minimum | Counterparty D
If credit rating is investment grade, fair value of fuel derivative level at which:
Fair value of fuel derivative levels at which cash is provided to CP Threshold 1	(75)
Fair value of fuel derivative level at which cash is received from CP	125	[5]
If credit rating is non-investment grade, fair value of fuel derivative level at which:
Fair value of fuel derivative levels at which cash is provided to CP Threshold 1		[3]
Fair value of fuel derivative level at which cash is received from CP		[3]
Minimum | Counterparty E
Schedule Of Fair Values Of Fuel Derivatives Amounts Posted As Collateral And Collateral Posting Thresholds [Line Items]
Option to substitute LC for cash	(50)	[4]
If credit rating is investment grade, fair value of fuel derivative level at which:
Fair value of fuel derivative levels at which cash is provided to CP Threshold 1	(50)
Fair value of fuel derivative level at which cash is received from CP	200
If credit rating is non-investment grade, fair value of fuel derivative level at which:
Fair value of fuel derivative levels at which cash is provided to CP Threshold 1		[3]
Fair value of fuel derivative level at which cash is received from CP		[3]
Minimum | Counterparty F
If credit rating is investment grade, fair value of fuel derivative level at which:
Fair value of fuel derivative levels at which cash is provided to CP Threshold 1	(50)
Fair value of fuel derivative level at which cash is received from CP	30
If credit rating is non-investment grade, fair value of fuel derivative level at which:
Fair value of fuel derivative levels at which cash is provided to CP Threshold 1		[3]
Fair value of fuel derivative level at which cash is received from CP		[3]
Maximum | Counterparty A
Schedule Of Fair Values Of Fuel Derivatives Amounts Posted As Collateral And Collateral Posting Thresholds [Line Items]
Option to substitute LC for aircraft	(740)	[2]
If credit rating is investment grade, fair value of fuel derivative level at which:
Fair value of fuel derivative levels at which cash is provided to CP Threshold 1	(340)
Fair value of fuel derivative levels at which aircraft or cash collateral is pledged to CP	(740)	[2]
If credit rating is non-investment grade, fair value of fuel derivative level at which:
Fair value of fuel derivative levels at which cash is provided to CP Threshold 1	(340)
Fair value of fuel derivative levels at which aircraft collateral is pledged to CP	(740)
Maximum | Counterparty B
If credit rating is investment grade, fair value of fuel derivative level at which:
Fair value of fuel derivative levels at which cash is provided to CP Threshold 1	(125)
Fair value of fuel derivative levels at which aircraft or cash collateral is pledged to CP	(625)	[2]
If credit rating is non-investment grade, fair value of fuel derivative level at which:
Fair value of fuel derivative levels at which cash is provided to CP Threshold 1	(125)
Fair value of fuel derivative levels at which aircraft collateral is pledged to CP	(625)
Maximum | Counterparty C
Schedule Of Fair Values Of Fuel Derivatives Amounts Posted As Collateral And Collateral Posting Thresholds [Line Items]
Option to substitute LC for cash	$ (150)	[4]

[1] Individual counterparties with fair value of fuel derivatives <$20 million.

[2] The Company has the option of providing cash, letters of credit, or pledging aircraft as collateral. No cash, letters of credit, or aircraft were pledged as collateral with such counterparties as of March 31, 2013.

[3] Cash collateral is provided at 100 percent of fair value of fuel derivative contracts.

[4] The Company has the option of providing cash or letters of credit as collateral. No cash or letters of credit were pledged as collateral with such counterparties as of March 31, 2013.

[5] Thresholds may vary based on changes in credit ratings within investment grade.