Consolidated Statements of Income - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Income Statement [Abstract]
Revenues	$ 5,847	$ 6,693	$ 17,694	$ 19,301
Operating expenses:
Compensation and benefits	1,406	1,496	4,129	3,968
Fuel	863	1,272	2,660	3,409
Depreciation and amortization	657	636	1,957	1,883
Purchased services	615	670	1,836	2,008
Equipment rents	171	180	511	544
Materials and other	329	331	1,129	961
Total operating expenses	4,041	4,585	12,222	12,773
Operating income	1,806	2,108	5,472	6,528
Interest expense	269	258	782	767
Other (income) expense, net	(71)	(34)	(182)	(83)
Income before income taxes	1,608	1,884	4,872	5,844
Income Tax Expense (Benefit)	387	442	1,140	1,367
Net income	$ 1,221	$ 1,442	$ 3,732	$ 4,477