Consolidated Statements of Cash Flows (USD $) In Millions, unless otherwise specified	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012
OPERATING ACTIVITIES
Net income	$ 2,671	$ 2,440
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	1,465	1,408
Deferred income taxes	457	481
Long-term casualty and environmental liabilities, net	(7)	(157)
Contribution to defined benefit pension plan	(25)	(36)
Other, net	(47)	(149)
Changes in current assets and liabilities:
Accounts receivable, net	(143)	(93)
Materials and supplies	0	(47)
Other current assets	(72)	(47)
Accounts payable and other current liabilities	(157)	107
Net cash provided by operating activities	4,142	3,907
INVESTING ACTIVITIES
Capital expenditures excluding equipment	(2,174)	(1,969)
Acquisition of equipment	(640)	(834)
Other, net	14	(87)
Net cash used for investing activities	(2,800)	(2,890)
FINANCING ACTIVITIES
Proceeds from issuance of long-term debt	3,000	2,500
Payments on long-term debt	(399)	(437)
Cash distributions	(2,900)	(2,750)
Other, net	(28)	(31)
Net cash used for financing activities	(327)	(718)
Increase in cash and cash equivalents	1,015	299
Cash and cash equivalents:
Beginning of period	1,794	1,960
End of period	2,809	2,259
SUPPLEMENTAL CASH FLOW INFORMATION
Interest paid, net of amounts capitalized	622	554
Capital investments accrued but not yet paid	144	151
Income taxes paid, net of refunds	$ 1,198	$ 807