AOCI - Reclassification out of Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Reclassification Out of Accumulated Other Comprehensive Income (Loss) [Line Items]
Fuel and oil	$ 870	$ 1,015
Other (gains) losses, net	(28)	(2)
Less: Tax Expense	50	$ (117)
Interest rate derivatives
Reclassification Out of Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification to earnings	0
Reclassification out of Accumulated Other Comprehensive Income (Loss) | Fuel derivatives
Reclassification Out of Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification to earnings	(24)
Less: Tax Expense	5
Net of Tax	19
Fuel derivatives | Reclassification out of Accumulated Other Comprehensive Income (Loss)
Reclassification Out of Accumulated Other Comprehensive Income (Loss) [Line Items]
Fuel and oil	22
Other (gains) losses, net	$ 2