REVENUE RECOGNITION - Narrative (Details) - USD ($) $ in Billions |
9 Months Ended | |
|---|---|---|
Sep. 30, 2024 |
Sep. 30, 2023 |
|
| Revenue from Contract with Customer [Abstract] | ||
| Revenue recognized that was previously deferred | $ 6.2 | $ 6.7 |
| Cash sales of mileage credits | $ 5.5 | $ 5.2 |
| Redemption period for majority of new miles (in years) | 2 years | |