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Financial Derivative Instruments Narrative (Details) - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2019 | Sep. 30, 2018 | Sep. 30, 2019 | Sep. 30, 2018
Derivative [Line Items] |  |  |  |
Premiums paid for fuel derivative contracts | $ 20 | $ 34 | $ 75 | $ 101
Percentage of actual consumption hedged | 66.00% |  | 76.00% |
Current Unrealized Net Losses in OCI | $ 43 |  | $ 43 |
Maximum sum of derivatives of counterparty to be included in other (less than $7 million) | $ 7 |  | $ 7 |
Maximum cash collateral provided as a percentage of derivative contract value (in hundredths) | 100.00% |  | 100.00% |
Maximum letter of credit percent of collateral | 100.00% |  | 100.00% |
Fuel derivatives |  |  |  |
Derivative [Line Items] |  |  |  |
Cash collateral provided by or held from CP | $ 0 |  | $ 0 |
Interest rate derivatives |  |  |  |
Derivative [Line Items] |  |  |  |
Cash collateral provided by or held from CP | $ 0 |  | $ 0 |
Remainder of Current Year |  |  |  |
Derivative [Line Items] |  |  |  |
Percent of fuel consumption hedged | 65.00% |  | 65.00% |

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- Definition Represents percentage of cash collateral provided on the fair value of fuel derivative contracts when credit rating is non-investment grade. + References No definition available. + Details
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- Definition Represents the percentage of cash collateral that can be provided with a letter of credit. + References No definition available. + Details
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- Definition Maximum sum of derivatives of a counterparty to be included in Other and no risk of the Company posting collateral. + References No definition available. + Details
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- Definition Percentage of actual consumption hedged + References No definition available. + Details
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- Definition The aggregate fair value of assets that are already posted, at the end of the reporting period, as collateral for derivative instruments with credit-risk-related contingent features. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4H -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5624258-113959 + Details
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- Definition The premium (cost) of a hedge, expensed during the period. + References No definition available. + Details
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
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- Definition The percentage of expected requirements covered by the aggregate notional amount of derivative contracts expressed in nonmonetary units. For example, the number of barrels specified in a fuel oil forward purchase contract as a percentage of expected need. + References No definition available. + Details
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- Definition The estimated net amount of unrealized gains or losses on price risk cash flow hedges as of the balance sheet date expected to be reclassified to earnings within the next twelve months. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 30 -Section 50 -Paragraph 1 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=112277219&loc=d3e80748-113994 + Details
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- Details
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- Details
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