Revenue - Roll Forward of Frequent Flyer Deferred Revenue (Details) - Frequent Flyer - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Frequent Flyer Deferred Revenue [Roll Forward]
Total Frequent flyer deferred revenue - beginning balance	$ 7,353	$ 7,024	$ 7,143	$ 6,675
Total miles awarded	884	816	2,643	2,465
Travel miles redeemed	(842)	(740)	(2,325)	(1,983)
Non-travel miles redeemed	(24)	(24)	(90)	(81)
Total Frequent flyer deferred revenue - ending balance	$ 7,371	$ 7,076	$ 7,371	$ 7,076

Amount of obligation to transfer good or service to customer for which consideration has been received or is receivable.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479837/606-10-45-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 8
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479806/606-10-50-8

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479837/606-10-45-2

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