Comprehensive Income - Reclassifications (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Reclassification Out of Accumulated Other Comprehensive Income (Loss) [Line Items]
Fuel and oil	$ 1,636	$ 803	$ 2,640	$ 1,272
Less: Tax expense	276	154	178	185
Interest expense	93	116	186	229
Net income	760	$ 348	482	$ 463
Reclassification to earnings
Reclassification Out of Accumulated Other Comprehensive Income (Loss) [Line Items]
Net income	(233)		(387)
Fuel derivative contracts | Fuel and Interest Rate Derivatives | Reclassification to earnings
Reclassification Out of Accumulated Other Comprehensive Income (Loss) [Line Items]
Fuel and oil	(306)		(508)
Less: Tax expense	(71)		(119)
Net income	(235)		(389)
Interest rate derivatives | Fuel and Interest Rate Derivatives | Reclassification to earnings
Reclassification Out of Accumulated Other Comprehensive Income (Loss) [Line Items]
Less: Tax expense	0		1
Interest expense	2		3
Net income	$ 2		$ 2