Consolidated Statements of Cash Flows (USD $) In Millions, unless otherwise specified	9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011
OPERATING ACTIVITIES
Net income	$ 2,440	$ 2,063
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	1,408	1,350
Deferred income taxes	481	1,098
Long-term casualty and environmental liabilities, net	(157)	(13)
Contribution to defined benefit pension plan	(36)	0
Other, net	(149)	(183)
Changes in current assets and liabilities:
Accounts receivable, net	(93)	(181)
Materials and supplies	(47)	(60)
Other current assets	(47)	(92)
Accounts payable and other current liabilities	107	308
Net cash provided by operating activities	3,907	4,290
INVESTING ACTIVITIES
Capital expenditures excluding equipment	(1,840)	(1,852)
Acquisition of equipment	(834)	(476)
Other, net	(216)	(168)
Net cash used for investing activities	(2,890)	(2,496)
FINANCING ACTIVITIES
Proceeds from issuance of long-term debt	2,500	1,500
Payments on long-term debt	(437)	(557)
Cash distributions	(2,750)	(2,750)
Other, net	(31)	(15)
Net cash used for financing activities	(718)	(1,822)
Increase (Decrease) in cash and cash equivalents	299	(28)
Cash and cash equivalents:
Beginning of period	1,960	2,087
End of period	2,259	2,059
SUPPLEMENTAL CASH FLOW INFORMATION
Interest paid, net of amounts capitalized	554	514
Capital investments accrued but not yet paid	151	155
Income taxes paid, net of refunds	807	(237)
Non-cash asset financing	$ 0	$ 1