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Financial Derivative Instruments - Location and Amount Recognized in Income by Hedging Relationship (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024
Cash Flow Hedging | Fuel derivative contracts
Derivative [Line Items]
Amount of loss reclassified from AOCI into income	$ 29	$ (1)
Fuel and oil
Derivative [Line Items]
Total	38	22
Fuel and oil | Cash Flow Hedging | Fuel derivative contracts
Derivative [Line Items]
Amount of loss reclassified from AOCI into income	38	22
Fuel and oil | Cash Flow Hedging | Other
Derivative [Line Items]
Amount of loss reclassified from AOCI into income	0	0
Other operating expenses
Derivative [Line Items]
Total	1	2
Other operating expenses | Cash Flow Hedging | Fuel derivative contracts
Derivative [Line Items]
Amount of loss reclassified from AOCI into income	0	0
Other operating expenses | Cash Flow Hedging | Other
Derivative [Line Items]
Amount of loss reclassified from AOCI into income	$ 1	$ 2

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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

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 40
-Name Accounting Standards Codification
-Section 50
-Paragraph 5
-Subparagraph (f)
-Publisher FASB
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Aggregate net gain (loss) on all derivative instruments recognized in earnings during the period, before tax effects.

+ References

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-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4A
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-Publisher FASB
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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

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