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Accumulated Other Comprehensive Income (Loss) - Reclassification out of Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items] |  |  |
Interest Expense | $ 131 | $ 114 | $ 122
Fuel and oil | 4,616 | 4,076 | 3,801
Less: Tax Expense | 699 | $ (92) | $ 1,267
Reclassification out of Accumulated Other Comprehensive Income |  |  |
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items] |  |  |
Net of tax | (20) |  |
Fuel derivatives | Reclassification out of Accumulated Other Comprehensive Income |  |  |
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items] |  |  |
Fuel and oil | (33) |  |
Less: Tax Expense | (8) |  |
Net of tax | (25) |  |
Interest rate derivatives | Reclassification out of Accumulated Other Comprehensive Income |  |  |
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items] |  |  |
Interest Expense | 6 |  |
Less: Tax Expense | 1 |  |
Net of tax | $ 5 |  |

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- Definition Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 22 -Subparagraph (h) -URI http://asc.fasb.org/extlink&oid=115929826&loc=d3e8736-108599 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.4-08(h)) -URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 20 -Section 45 -Paragraph 2 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=109238882&loc=d3e38679-109324 + Details
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