REVENUE RECOGNITION - Loyalty Program Liability (Details) - Loyalty program deferred revenue - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Loyalty Program
Current and noncurrent deferred revenue, beginning	$ 8,420	$ 7,882	$ 7,559
Miles earned	4,463	4,173	3,419
Travel miles redeemed	(3,841)	(3,462)	(2,898)
Non-travel miles redeemed	(216)	(173)	(198)
Current and noncurrent deferred revenue, ending	$ 8,826	$ 8,420	$ 7,882

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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