Consolidated Statements of Income - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Income Statement [Abstract]
Revenues	$ 5,176	$ 6,021	$ 15,195	$ 17,676
Operating expenses:
Compensation and benefits	1,120	1,337	3,357	4,071
Purchased services	633	687	1,859	2,087
Depreciation and amortization	621	602	1,848	1,788
Fuel	394	725	1,335	2,211
Equipment rents	174	195	493	573
Materials and other	223	295	739	980
Total operating expenses	3,165	3,841	9,631	11,710
Operating income	2,011	2,180	5,564	5,966
Interest expense	257	271	779	806
Other (income) expense, net	(23)	(32)	(70)	(219)
Income before income taxes	1,777	1,941	4,855	5,379
Income tax expense	430	475	1,187	1,322
Net income	$ 1,347	$ 1,466	$ 3,668	$ 4,057