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Financial Derivative Instruments - Collateral by Balance Sheet Location (Details) - Fuel derivatives - USD ($) $ in Millions | Dec. 31, 2019 | Dec. 31, 2018
--- | --- | ---
Derivative [Line Items] |  |
Collateral Already Posted, Aggregate Fair Value | $ 25 |
Prepaid expenses and other current assets |  |
Derivative [Line Items] |  |
Total Collateral Already Received Aggregate Fair Value | 10 | $ 0
Other Assets |  |
Derivative [Line Items] |  |
Total Collateral Already Received Aggregate Fair Value | $ 15 | $ 0

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- Definition Total cash, current and noncurrent, that is already received, at the end of the reporting period, as collateral for derivative instruments. + 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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