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Financial Derivative Instruments - Collateral by Balance Sheet Location (Details) - Fuel derivatives - USD ($) $ in Millions | Jun. 30, 2020 | Dec. 31, 2019
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Prepaid expenses and other current assets |  |
Derivative [Line Items] |  |
Cash collateral deposits held from CP for fuel contracts - current | $ 1 | $ 10
Other Assets |  |
Derivative [Line Items] |  |
Cash collateral deposits held from CP for fuel contracts - non-current | $ 31 | $ 15

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- Definition Amount of obligation to return cash collateral under master netting arrangements offset against derivative assets. + 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 (b) -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 815 -SubTopic 10 -Section 45 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=117331979&loc=d3e41228-113958 + Details
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