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Financial Derivative Instruments - Fair Values of Fuel Derivatives Amounts Posted as Collateral (Details) - Fuel derivatives $ in Millions | Mar. 31, 2019 USD ($)
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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 | $ 254 |
Cash collateral held from (by) CP | 15 |
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 Asset, Fair Value, Amount Not Offset Against Collateral | 68 |
Cash collateral held from (by) CP | 15 |
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 Asset, Fair Value, Amount Not Offset Against Collateral | 52 |
Cash collateral held from (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] |  |
Derivative Asset, Fair Value, Amount Not Offset Against Collateral | 73 |
Cash collateral held from (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] |  |
Derivative Asset, Fair Value, Amount Not Offset Against Collateral | 22 |
Cash collateral held from (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] |  |
Derivative Asset, Fair Value, Amount Not Offset Against Collateral | 12 |
Cash collateral held from (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] |  |
Derivative Asset, Fair Value, Amount Not Offset Against Collateral | 13 |
Cash collateral held from (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] |  |
Derivative Asset, Fair Value, Amount Not Offset Against Collateral | 14 | [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 | [3]
Fair value of fuel derivative levels at which aircraft or cash collateral is pledged to CP | (200) | [4]
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 |  | [5]
Fair value of fuel derivative levels at which aircraft or cash collateral is pledged to CP | (200) |
Minimum | 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 | (50) |
Fair value of fuel derivative levels at which cash is provided to CP Threshold 2 |  |
Fair value of fuel derivative level at which cash is received from CP | 150 | [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 |  | [5]
Fair value of fuel derivative levels at which cash is provided to CP Threshold 2 |  |
Fair value of fuel derivative level at which cash is received from CP |  | [5]
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 aircraft | (150) | [6]
Fair Value Of Fuel Derivative Levels In Which Letters Of Credit May Be Substituted 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) | [3]
Fair value of fuel derivative levels at which cash is provided to CP Threshold 2 | (550) | [3]
Fair value of fuel derivative level at which cash is received from CP | 250 | [3]
Fair value of fuel derivative levels at which aircraft or cash collateral is pledged to CP | (150) | [6]
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 |  | [5]
Fair value of fuel derivative levels at which aircraft or cash collateral is pledged to CP | (150) |
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) | [6]
Fair Value Of Fuel Derivative Levels In Which Letters Of Credit May Be Substituted For Cash Threshold 1 | (125) | [7]
Option to substitute LC for cash Threshold 2 | (550) | [7]
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) | [3]
Fair value of fuel derivative levels at which cash is provided to CP Threshold 2 | (550) | [3]
Fair value of fuel derivative level at which cash is received from CP | 125 | [3]
Fair value of fuel derivative levels at which aircraft or cash collateral is pledged to CP | (150) | [6]
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 |  | [5]
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] |  |
Fair Value Of Fuel Derivative Levels In Which Letters Of Credit May Be Substituted For Cash Threshold 1 |  | [7]
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 | (100) | [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 |  | [5]
Fair value of fuel derivative level at which cash is received from CP |  | [5]
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 | (70) | [3]
Fair value of fuel derivative level at which cash is received from CP | 70 | [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 |  | [5]
Fair value of fuel derivative level at which cash is received from CP |  | [5]
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]
Fair Value Of Fuel Derivative Levels In Which Letters Of Credit May Be Substituted 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) | [4]
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 C |  |
Schedule Of Fair Values Of Fuel Derivatives Amounts Posted As Collateral And Collateral Posting Thresholds [Line Items] |  |
Option to substitute LC for aircraft | (550) | [6]
Fair Value Of Fuel Derivative Levels In Which Letters Of Credit May Be Substituted 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) | [3]
Fair value of fuel derivative levels at which aircraft or cash collateral is pledged to CP | (550) | [6]
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 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) | [6]
Fair Value Of Fuel Derivative Levels In Which Letters Of Credit May Be Substituted For Cash Threshold 1 | (150) | [7]
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) | [3]
Fair value of fuel derivative levels at which aircraft or cash collateral is pledged to CP | (550) | [6]
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 < $10 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] | Thresholds may vary based on changes in credit ratings within investment grade.
[4] | The Company has the option of providing cash or pledging aircraft as collateral.
[5] | Cash collateral is provided at 100 percent of fair value of fuel derivative contracts.
[6] | The Company has the option of providing cash, letters of credit, or pledging aircraft as collateral.
[7] | The Company has the option to substitute letters of credit for 100 percent of cash collateral requirement.

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