Consolidated Statements of Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Revenues	$ 21,967	$ 23,239	$ 22,014
Operating expenses:
Compensation and benefits	5,043	5,023	4,651
Fuel	2,656	4,478	4,503
Purchased services	2,546	2,592	2,418
Depreciation and amortization	2,001	2,123	1,973
Equipment rents	801	867	822
Materials and other	1,196	1,143	980
Total operating expenses	14,243	16,226	15,347
Operating income	7,724	7,013	6,667
Interest expense	928	833	729
Other expense, net	21	11	10
Income before income taxes	6,775	6,169	5,928
Income tax expense	2,527	2,300	2,135
Net income	$ 4,248	$ 3,869	$ 3,793