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Financial Derivative Instruments - Location and Amount Recognized in Income by Hedging Relationship (Details) - USD ($) $ in Millions | 3 Months Ended
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Mar. 31, 2024 | Mar. 31, 2023
Cash Flow Hedging |  |
Derivative [Line Items] |  |
Amount of (gain) loss reclassified from AOCI into income | $ (1) | $ 127
Cash Flow Hedging | Fuel derivative contracts |  |
Derivative [Line Items] |  |
Amount of (gain) loss reclassified from AOCI into income | (1) | 125
Cash Flow Hedging | Other |  |
Derivative [Line Items] |  |
Amount of (gain) loss reclassified from AOCI into income | 0 | 2
Fuel and oil |  |
Derivative [Line Items] |  |
Derivatives designated as hedging instruments | 22 | (28)
Fuel and oil | Cash Flow Hedging | Fuel derivative contracts |  |
Derivative [Line Items] |  |
Amount of (gain) loss reclassified from AOCI into income | 22 | (28)
Fuel and oil | Cash Flow Hedging | Other |  |
Derivative [Line Items] |  |
Amount of (gain) loss reclassified from AOCI into income | 0 | 0
Other operating expenses |  |
Derivative [Line Items] |  |
Derivatives designated as hedging instruments | 2 | 2
Other operating expenses | Cash Flow Hedging | Fuel derivative contracts |  |
Derivative [Line Items] |  |
Amount of (gain) loss reclassified from AOCI into income | 0 | 0
Other operating expenses | Cash Flow Hedging | Other |  |
Derivative [Line Items] |  |
Amount of (gain) loss reclassified from AOCI into income | $ 2 | $ 2

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- Definition Aggregate net gain (loss) on all derivative instruments recognized in earnings during the period, before tax effects. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4A -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480434/815-10-50-4A + Details
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- Definition Amount, before tax, of reclassification of gain (loss) from accumulated other comprehensive income (AOCI) for derivative instrument designated and qualifying as cash flow hedge included in assessment of hedge effectiveness. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 220 -SubTopic 10 -Name Accounting Standards Codification -Section 45 -Paragraph 11 -Publisher FASB -URI https://asc.fasb.org//1943274/2147482790/220-10-45-11 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 220 -SubTopic 10 -Name Accounting Standards Codification -Section 45 -Paragraph 15 -Publisher FASB -URI https://asc.fasb.org//1943274/2147482790/220-10-45-15 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Name Accounting Standards Codification -Section 50 -Paragraph 4C -Subparagraph (c) -SubTopic 10 -Topic 815 -Publisher FASB -URI https://asc.fasb.org//1943274/2147480434/815-10-50-4C + Details
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