Consolidated Statements of Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Income Statement [Abstract]
Revenues	$ 23,876	$ 25,888	$ 23,282
Operating expenses:
Compensation and benefits	5,551	5,321	4,767
Fuel	3,684	4,581	2,766
Depreciation and amortization	2,625	2,528	2,456
Purchased services	2,396	2,697	2,715
Equipment rents	699	720	677
Materials and other	1,522	1,441	1,103
Total operating expenses	16,477	17,288	14,484
Operating income	7,399	8,600	8,798
Interest expense	1,048	1,025	1,032
Other (income) expense, net	(263)	(133)	(95)
Income before income taxes	6,614	7,708	7,861
Income tax expense	1,527	1,762	1,871
Net income	$ 5,087	$ 5,946	$ 5,990