Consolidated Statements of Income - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Income Statement [Abstract]
Revenues	$ 5,968	$ 5,401
Operating expenses:
Compensation and benefits	1,241	1,183
Fuel	861	550
Purchased services	668	665
Depreciation and amortization	627	619
Equipment rents	179	171
Materials and other	351	324
Total operating expenses	3,927	3,512
Operating income	2,041	1,889
Interest expense	255	258
Other (income) expense, net	(23)	(28)
Income before income taxes	1,809	1,659
Income tax expense	438	408
Net income	$ 1,371	$ 1,251