Financial Derivative Instruments - Fair Values of Fuel Derivatives Amounts Posted as Collateral (Details) - Fuel derivatives $ in Millions	Mar. 31, 2016 USD ($)
Schedule Of Fair Values Of Fuel Derivatives Amounts Posted As Collateral And Collateral Posting Thresholds [Line Items]
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	$ (1,408)
Cash collateral held from (by) CP	(1,067)
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]
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	(565)
Cash collateral held from (by) CP	(544)
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]
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	(183)
Cash collateral held from (by) CP	(140)
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]
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	(118)
Cash collateral held from (by) CP	(12)
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]
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	(415)
Cash collateral held from (by) CP	(355)
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]
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	(145)
Cash collateral held from (by) CP	(31)
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]
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	(15)
Cash collateral held from (by) CP	15
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]
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	(3)	[1]
Cash collateral held from (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	(200)	[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	(600)
Fair value of fuel derivative level at which cash is received from CP	50
Fair value of fuel derivative levels at which aircraft or cash collateral is pledged to CP	(200)	[3]
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	$ (600)
Fair value of fuel derivative level at which cash is received from CP		[4]
Fair value of fuel derivative levels at which aircraft or cash collateral is pledged to CP	$ (200)
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)	[5]
Option to substitute LC for cash Threshold 1	(500)	[6]
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)	[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	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		[4]
Fair value of fuel derivative levels at which aircraft or cash 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	(225)	[6]
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 level at which cash is received from CP	$ 175	[7]
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		[4]
Fair value of fuel derivative level at which cash is received from CP		[4]
Minimum | Counterparty D
Schedule Of Fair Values Of Fuel Derivatives Amounts Posted As Collateral And Collateral Posting Thresholds [Line Items]
Option to substitute LC for aircraft	$ (150)	[5]
Option to substitute LC for cash Threshold 1	(75)	[6]
Option to substitute LC for cash Threshold 2	(550)	[6]
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 levels at which cash is provided to CP Threshold 2	(550)
Fair value of fuel derivative level at which cash is received from CP	250
Fair value of fuel derivative levels at which aircraft or cash collateral is pledged to CP	(150)	[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	0
Fair value of fuel derivative levels at which cash is provided to CP Threshold 2	$ (550)
Fair value of fuel derivative level at which cash is received from CP		[4]
Fair value of fuel derivative levels at which aircraft or cash collateral is pledged to CP	$ (150)
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	(150)	[5]
Option to substitute LC for cash Threshold 1	(75)	[6]
Option to substitute LC for cash Threshold 2	(550)	[6]
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 cash is provided to CP Threshold 2	(550)
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	(150)	[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	0
Fair value of fuel derivative levels at which cash is provided to CP Threshold 2	$ (550)
Fair value of fuel derivative level at which cash is received from CP		[4]
Fair value of fuel derivative levels at which aircraft or cash collateral is pledged to CP	$ (150)
Minimum | Counterparty F
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		[8]
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 level at which cash is received from CP	$ 0
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		[4]
Fair value of fuel derivative level at which cash is received from CP		[4]
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	$ (600)	[2]
Option to substitute LC for cash Threshold 1
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	$ (200)
Fair value of fuel derivative levels at which aircraft or cash collateral is pledged to CP	(600)	[3]
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	(200)
Fair value of fuel derivative levels at which aircraft or cash collateral is pledged to CP	(600)
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)	[5]
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)	[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	(100)
Fair value of fuel derivative levels at which aircraft or cash 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	(275)	[6]
Maximum | Counterparty D
Schedule Of Fair Values Of Fuel Derivatives Amounts Posted As Collateral And Collateral Posting Thresholds [Line Items]
Option to substitute LC for aircraft	(550)	[5]
Option to substitute LC for cash Threshold 1	(150)	[6]
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	(150)
Fair value of fuel derivative levels at which aircraft or cash collateral is pledged to CP	(550)	[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	(150)
Fair value of fuel derivative levels at which aircraft or cash collateral is pledged to CP	(550)
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	(550)	[5]
Option to substitute LC for cash Threshold 1	(150)	[6]
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	(150)
Fair value of fuel derivative levels at which aircraft or cash collateral is pledged to CP	(550)	[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	(150)
Fair value of fuel derivative levels at which aircraft or cash collateral is pledged to CP	$ (550)

[1] Individual counterparties with fair value of fuel derivatives <$5 million.

[2] The Company has the option of providing letters of credit in addition to aircraft collateral if the appraised value of the aircraft does not meet the collateral requirements.

[3] The Company has the option of providing cash or pledging aircraft as collateral.

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

[5] The Company has the option of providing cash, letters of credit, or pledging aircraft as collateral.

[6] The Company has the option of providing cash or letters of credit as collateral.

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

[8] The Company has the option to substitute letters of credit for 100 percent of cash collateral requirement.