Consolidated Statements of Cash Flows (USD $) In Millions, unless otherwise specified	6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013
OPERATING ACTIVITIES
Net income	$ 1,640	$ 1,682
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	1,038	972
Deferred income taxes	77	295
Long-term casualty and environmental liabilities, net	(21)	(13)
Contribution to defined benefit pension plan	0	(25)
Other, net	(242)	(90)
Changes in current assets and liabilities:
Accounts receivable, net	(23)	(111)
Materials and supplies	(31)	(5)
Other current assets	(97)	(112)
Accounts payable and other current liabilities	411	(422)
Net cash provided by operating activities	2,752	2,171
INVESTING ACTIVITIES
Capital expenditures excluding equipment	(1,529)	(1,304)
Acquisition of equipment	(628)	(369)
Other, net	(40)	3
Net cash used for investing activities	(2,197)	(1,670)
FINANCING ACTIVITIES
Proceeds from issuance of long-term debt	1,500	1,500
Payments on long-term debt	(589)	(111)
Cash distributions	(1,750)	(2,000)
Other, net	(15)	(12)
Net cash used for financing activities	(854)	(623)
Decrease in cash and cash equivalents	(299)	(122)
Cash and cash equivalents:
Beginning of period	2,225	1,794
End of period	1,926	1,672
SUPPLEMENTAL CASH FLOW INFORMATION
Interest paid, net of amounts capitalized	425	375
Capital investments accrued but not yet paid	196	147
Income taxes paid, net of refunds	$ 496	$ 1,042