REVENUE RECOGNITION - Narrative (Details) - USD ($) $ in Billions |
3 Months Ended | |
|---|---|---|
Mar. 31, 2024 |
Mar. 31, 2023 |
|
| Revenue from Contract with Customer [Abstract] | ||
| Revenue recognized that was previously deferred | $ 3.9 | $ 3.9 |
| Cash sales of mileage credits | $ 1.8 | $ 1.7 |
| Redemption period for majority of new miles (in years) | 2 years | |