Condensed Consolidated Statements of Income (Unaudited) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Operating revenues [Abstract]
Freight revenues	$ 4,913	$ 4,595	$ 9,736	$ 8,843
Other revenues	308	263	597	505
Total operating revenues	5,221	4,858	10,333	9,348
Operating expenses [Abstract]
Compensation and benefits	1,151	1,166	2,362	2,333
Fuel	882	904	1,808	1,730
Purchased services and materials	542	516	1,068	991
Depreciation	433	401	860	796
Equipment and other rents	299	283	595	585
Other	190	196	406	384
Total operating expenses	3,497	3,466	7,099	6,819
Operating income	1,724	1,392	3,234	2,529
Other income (Note 6)	21	26	37	41
Interest expense	(135)	(148)	(270)	(289)
Income before income taxes	1,610	1,270	3,001	2,281
Income taxes	(608)	(485)	(1,136)	(857)
Net income	$ 1,002	$ 785	$ 1,865	$ 1,424
Share and Per Share (Note 8) [Abstract]
Earnings per share - basic	$ 2.11	$ 1.61	$ 3.92	$ 2.91
Earnings per share - diluted	$ 2.10	$ 1.59	$ 3.89	$ 2.89
Weighted average number of shares - basic	473.8	488.4	475.8	489.0
Weighted average number of shares - diluted	477.2	492.4	479.3	493.3
Dividends declared per share	$ 0.60	$ 0.475	$ 1.20	$ 0.855