Consolidated Statements of Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenues	$ 23,855	$ 21,387	$ 19,829
Operating expenses:
Compensation and benefits	5,394	5,023	4,809
Fuel	3,346	2,518	1,934
Purchased services	2,870	2,514	2,418
Depreciation and amortization	2,317	2,352	2,128
Equipment rents	732	784	766
Materials and other	1,396	903	1,129
Total operating expenses	16,055	14,094	13,184
Operating income	7,800	7,293	6,645
Interest expense	1,041	1,016	992
Other expense, net	(104)	(51)	(40)
Income before income taxes	6,863	6,328	5,693
Income tax expense	1,644	(4,972)	2,124
Net income	$ 5,219	$ 11,300	$ 3,569