Consolidated Statements of Income - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Income Statement [Abstract]
Revenues	$ 6,021	$ 6,147	$ 17,676	$ 17,649
Operating expenses:
Compensation and benefits	1,337	1,378	4,071	4,021
Fuel	725	859	2,211	2,456
Purchased services	687	718	2,087	2,124
Depreciation and amortization	602	580	1,788	1,726
Equipment rents	195	183	573	542
Materials and other	295	320	980	1,041
Total operating expenses	3,841	4,038	11,710	11,910
Operating income	2,180	2,109	5,966	5,739
Interest expense	271	262	806	774
Other (income) expense, net	(32)	(32)	(219)	(82)
Income before income taxes	1,941	1,879	5,379	5,047
Income tax expense	475	486	1,322	1,200
Net income	$ 1,466	$ 1,393	$ 4,057	$ 3,847