Consolidated Statements of Cash Flows (USD $) In Millions, unless otherwise specified	6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011
OPERATING ACTIVITIES
Net income	$ 1,503	$ 1,297
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	933	896
Deferred income taxes	290	431
Long-term casualty and environmental liabilities, net	(66)	(27)
Contribution to defined benefit pension plan	(36)	0
Other, net	(116)	(136)
Changes in current assets and liabilities:
Accounts receivable, net	24	(77)
Materials and supplies	(38)	(78)
Other current assets	(104)	(157)
Accounts payable and other current liabilities	(83)	435
Net cash provided by operating activities	2,307	2,584
INVESTING ACTIVITIES
Capital expenditures excluding equipment	(1,164)	(1,101)
Acquisition of equipment	(564)	(261)
Other, net	(211)	(151)
Net cash used for investing activities	(1,939)	(1,513)
FINANCING ACTIVITIES
Proceeds from issuance of long-term debt	1,250	750
Payments on long-term debt	(98)	(116)
Cash distributions	(1,750)	(2,000)
Other, net	(12)	(9)
Net cash used for financing activities	(610)	(1,375)
Decrease in cash and cash equivalents	(242)	(304)
Cash and cash equivalents:
Beginning of period	1,960	2,087
End of period	1,718	1,783
SUPPLEMENTAL CASH FLOW INFORMATION
Interest paid, net of amounts capitalized	341	329
Capital investments accrued but not yet paid	143	115
Income taxes paid, net of refunds	503	(238)
Non-cash asset financing	$ 0	$ 1