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Significant Accounting Policies - Roll Forward of Frequent Flier Deferred Revenue (Details) - Frequent Flyer - USD ($) $ in Millions | 12 Months Ended
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Dec. 31, 2023 | Dec. 31, 2022
Movement in Deferred Revenue [Roll Forward] |  |
Total Frequent flyer deferred revenue - beginning balance | $ 6,675 | $ 6,282
Total miles awarded | 3,297 | 2,558
Travel miles redeemed | (2,723) | (2,079)
Non-travel miles redeemed | (106) | (86)
Total Frequent flyer deferred revenue - ending balance | $ 7,143 | $ 6,675

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- Details
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