REVENUE RECOGNITION - Narrative (Details) - USD ($) $ in Billions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Revenue from Contract with Customer [Abstract]
Revenue recognized that was previously recorded in air traffic liability	$ 4.2	$ 2.2	$ 3.1
Marketing contracts initial terms, minimum (in years)	3 years
Marketing contracts initial terms, maximum (in years)	11 years
Cash sales of miles from marketing agreements	$ 5.7	$ 4.1	$ 2.9
Majority of new miles, redemption period (in years)	2 years