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Financial Derivative Instruments - Fair Values of Fuel Derivatives Amounts Posted as Collateral (Details) $ in Millions | Sep. 30, 2020 USD ($)
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Schedule Of Fair Values Of Fuel Derivatives Amounts Posted As Collateral And Collateral Posting Thresholds [Line Items] |  |
Letter of Credit Percent of Collateral | 100.00% |
Cash Collateral Percent Of Fair Value Fuel Derivatives Contracts | 100.00% |
Fuel derivatives |  |
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 | $ 109 |
Cash collateral held (from) by CP | 27 |
Letters of credit (LC) | 0 |
Counterparty A | Fuel derivatives |  |
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 | 24 |
Cash collateral held (from) by CP | 27 |
Letters of credit (LC) | 0 |
Counterparty B | Fuel derivatives |  |
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 |
Cash collateral held (from) by CP | 0 |
Letters of credit (LC) | 0 |
Counterparty C | Fuel derivatives |  |
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 | 28 |
Cash collateral held (from) by CP | 0 |
Letters of credit (LC) | 0 |
Counterparty D | Fuel derivatives |  |
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 |
Letters of credit (LC) | 0 |
Counterparty E | Fuel derivatives |  |
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 | 11 |
Cash collateral held (from) by CP | 0 |
Letters of credit (LC) | 0 |
Counterparty F | Fuel derivatives |  |
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 | 10 |
Cash collateral held (from) by CP | 0 |
Letters of credit (LC) | 0 |
Counterparty Other | Fuel derivatives |  |
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 | 10 | [1]
Cash collateral held (from) by CP | 0 | [1]
Letters of credit (LC) | 0 | [1]
Minimum | Counterparty A | Fuel derivatives |  |
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 | [2]
Fair value of fuel derivative levels at which 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 cash collateral is pledged to CP | (200) |
Minimum | Counterparty B | Fuel derivatives |  |
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 | 150 | [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 |  | [4]
Fair value of fuel derivative level at which cash is received from CP |  | [4]
Minimum | Counterparty C | Fuel derivatives |  |
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 | (75) | [5]
Option to substitute LC for cash Threshold 2 | (550) | [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 | (75) | [2]
Fair value of fuel derivative levels at which cash is provided to CP Threshold 2 | (550) | [2]
Fair value of fuel derivative level at which cash is received from CP | 250 | [2]
Fair value of fuel derivative levels at which 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 cash collateral is pledged to CP | (150) |
Minimum | Counterparty D | Fuel derivatives |  |
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 | (125) | [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) | [2]
Fair value of fuel derivative levels at which cash is provided to CP Threshold 2 | (550) | [2]
Fair value of fuel derivative level at which cash is received from CP | (125) | [2]
Fair value of fuel derivative levels at which 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 cash collateral is pledged to CP | (150) |
Minimum | Counterparty E | Fuel derivatives |  |
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 |  | [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 | (40) |
Fair value of fuel derivative level at which cash is received from 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 |  | [4]
Fair value of fuel derivative level at which cash is received from CP |  | [4]
Minimum | Counterparty F | Fuel derivatives |  |
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 | (65) | [2]
Fair value of fuel derivative level at which cash is received from CP | 70 | [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 |  | [4]
Fair value of fuel derivative level at which cash is received from CP |  | [4]
Maximum | Counterparty A | Fuel derivatives |  |
If credit rating is investment grade, fair value of fuel derivative level at which: |  |
Fair value of fuel derivative levels at which 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 cash collateral is pledged to CP | (600) |
Maximum | Counterparty C | Fuel derivatives |  |
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) | [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 | (150) | [2]
Fair value of fuel derivative levels at which 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 cash collateral is pledged to CP | (550) |
Maximum | Counterparty D | Fuel derivatives |  |
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) | [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) | [2]
Fair value of fuel derivative levels at which 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 cash collateral is pledged to CP | $ (550) |
[1] | Individual counterparties with fair value of fuel derivatives < $9 million.
[2] | Thresholds may vary based on changes in credit ratings within investment grade.
[3] | The Company has the option of providing cash 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 or letters of credit as collateral.
[6] | The Company has the option to substitute letters of credit for 100 percent of cash collateral requirement.

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- Definition Fair Value Of Fuel Derivative Levels In Which Letters Of Credit May Be Substituted For Cash Threshold 1 + References No definition available. + Details
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- Definition Fair value, after offset of derivative liability, of financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset, before offset against an obligation to return collateral under a master netting arrangement. Includes assets elected not to be offset. Excludes assets not subject to a master netting arrangement. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 50 -Paragraph 3 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 55 -Paragraph 10 -URI http://asc.fasb.org/extlink&oid=99393222&loc=SL20226008-175313 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 55 -Paragraph 9 -URI http://asc.fasb.org/extlink&oid=99393222&loc=SL20226006-175313 Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 8 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=121590274&loc=d3e41678-113959 + Details
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