Comprehensive Income - Differences between Net Income and Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended				6 Months Ended
	Jun. 30, 2022	Mar. 31, 2022	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2022	Jun. 30, 2021
Condensed Statement of Income Captions [Line Items]
NET INCOME	$ 760		$ 348		$ 482	$ 463
Other, net of deferred taxes of $— and $—					0	(47)
Total other comprehensive income (loss)	(86)		196		417	260
COMPREHENSIVE INCOME	674	$ 225	544	$ 180	899	723
Other deferred taxes					0	(13)
Fuel derivative contracts
Condensed Statement of Income Captions [Line Items]
Unrealized gain (loss) on derivative instruments, net of deferred taxes	(95)		201		403	301
Derivative deferred taxes	(29)		61		122	92
Interest rate derivatives
Condensed Statement of Income Captions [Line Items]
Unrealized gain (loss) on derivative instruments, net of deferred taxes	9		(5)		14	6
Derivative deferred taxes	$ 3		$ (1)		$ 5	$ 1