Consolidated Statements of Income (USD $) In Millions, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Operating revenues [Abstract]
Freight revenues	$ 19,686	$ 18,508	$ 16,069
Other revenues	1,240	1,049	896
Total operating revenues	20,926	19,557	16,965
Operating expenses [Abstract]
Compensation and benefits	4,685	4,681	4,314
Fuel	3,608	3,581	2,486
Purchased services and materials	2,143	2,005	1,836
Depreciation	1,760	1,617	1,487
Equipment and other rents	1,197	1,167	1,142
Other	788	782	719
Total operating expenses	14,181	13,833	11,984
Operating income	6,745	5,724	4,981
Other income (Note 6)	108	112	54
Interest expense	(535)	(572)	(602)
Income before income taxes	6,318	5,264	4,433
Income taxes (Note 7)	(2,375)	(1,972)	(1,653)
Net income	$ 3,943	$ 3,292	$ 2,780
Share and Per Share (Note 8) [Abstract]
Earnings per share - basic	$ 8.33	$ 6.78	$ 5.58
Earnings per share - diluted	$ 8.27	$ 6.72	$ 5.53
Weighted average number of shares - basic	473.1	485.7	498.2
Weighted average number of shares - diluted	476.5	489.8	502.9
Dividends declared per share	$ 2.49	$ 1.93	$ 1.31