Financial Derivative Instruments - Fair Values of Fuel Derivatives Amounts Posted as Collateral (Details) (Fuel derivatives, USD $) In Millions, unless otherwise specified	Sep. 30, 2013
Schedule Of Fair Values Of Fuel Derivatives Amounts Posted As Collateral And Collateral Posting Thresholds [Line Items]
Fair value of fuel derivatives	$ 87
Cash collateral held by CP	0
Aircraft collateral pledged to CP	0
Letters of credit (LC)	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	19
Cash collateral held by CP	0
Aircraft collateral pledged to CP	0
Letters of credit (LC)	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	23
Cash collateral held by CP	0
Aircraft collateral pledged to CP	0
Letters of credit (LC)	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	12
Cash collateral held by CP	0
Aircraft collateral pledged to CP	0
Letters of credit (LC)	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	(3)
Cash collateral held by CP	0
Aircraft collateral pledged to CP	0
Letters of credit (LC)	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	17
Cash collateral held by CP	0
Aircraft collateral pledged to CP	0
Letters of credit (LC)	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	10
Cash collateral held by CP	0
Aircraft collateral pledged to CP	0
Letters of credit (LC)	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	9	[1]
Cash collateral held by CP	0	[1]
Aircraft collateral pledged to CP	0	[1]
Letters of credit (LC)	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	0
Fair value of fuel derivative levels at which cash is provided to CP Threshold 2	(700)
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	(300)
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	(100)	[2]
Option to substitute LC for cash Threshold 1	(500)
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 levels at which cash is provided to CP Threshold 2	(500)
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	(100)	[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	(500)
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	(100)
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 Threshold 1	(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 aircraft	250	[2]
Option to substitute LC for cash Threshold 1	(50)	[2]
Option to substitute LC for cash Threshold 2	(650)	[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	(50)
Fair value of fuel derivative levels at which cash is provided to CP Threshold 2	(650)
Fair value of fuel derivative level at which cash is received from CP	200
Fair value of fuel derivative levels at which aircraft or cash collateral is pledged to CP	(250)	[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	(650)
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	(250)
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	(300)
Fair value of fuel derivative levels at which aircraft collateral is pledged to CP	(700)
Maximum | 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	(500)	[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	(100)
Fair value of fuel derivative levels at which aircraft or cash collateral is pledged to CP	(500)	[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	(100)
Fair value of fuel derivative levels at which aircraft collateral is pledged to CP	(500)
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 Threshold 1	(150)	[4]
Maximum | Counterparty E
Schedule Of Fair Values Of Fuel Derivatives Amounts Posted As Collateral And Collateral Posting Thresholds [Line Items]
Option to substitute LC for aircraft	(650)	[2]
Option to substitute LC for cash Threshold 1	(250)	[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	(250)
Fair value of fuel derivative levels at which aircraft or cash collateral is pledged to CP	(650)	[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	(250)
Fair value of fuel derivative levels at which aircraft collateral is pledged to CP	$ (650)

[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 September 30, 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 September 30, 2013.

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