Consolidated Statements of Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenues	$ 21,387	$ 19,829	$ 21,967
Operating expenses:
Compensation and benefits	4,969	4,769	5,043
Fuel	2,518	1,934	2,656
Purchased services	2,514	2,418	2,546
Depreciation and amortization	2,352	2,128	2,001
Equipment rents	784	766	801
Materials and other	903	1,129	1,196
Total operating expenses	14,040	13,144	14,243
Operating income	7,347	6,685	7,724
Interest expense	1,016	992	928
Other expense, net	3	0	21
Income before income taxes	6,328	5,693	6,775
Income tax expense	(4,972)	2,124	2,527
Net income	$ 11,300	$ 3,569	$ 4,248