Consolidated Statements of Income (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Revenues	$ 22,014	$ 20,835	$ 19,548
Operating expenses:
Compensation and benefits	4,651	4,505	4,315
Fuel	4,503	4,459	4,267
Purchased services	2,418	2,374	2,218
Depreciation and amortization	1,973	1,889	1,807
Equipment rents	822	810	779
Materials and other	980	786	852
Total operating expenses	15,347	14,823	14,238
Operating income	6,667	6,012	5,310
Interest expense	729	623	560
Other expense, net	10	12	9
Income before income taxes	5,928	5,377	4,741
Income tax expense	2,135	2,005	1,769
Net income	$ 3,793	$ 3,372	$ 2,972