Consolidated Statements of Cash Flows - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
OPERATING ACTIVITIES
Net income	$ 2,454	$ 1,796
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	1,146	1,165
Deferred income taxes	144	232
Long-term casualty and environmental liabilities, net	(19)	(19)
Other, net	(93)	(113)
Changes in current assets and liabilities:
Accounts receivable, net	(14)	(17)
Materials and supplies	14	6
Other current assets	(104)	(17)
Accounts payable and other current liabilities	266	502
Net cash provided by operating activities	3,794	3,535
INVESTING ACTIVITIES
Capital expenditures excluding equipment	(1,224)	(1,296)
Acquisition of equipment	(72)	(200)
Purchases of investments and investments in time deposits	(13)	(8)
Proceeds from sales of investments and maturities of time deposits	17	15
Other, net	(108)	(235)
Net cash used for investing activities	(1,400)	(1,724)
FINANCING ACTIVITIES
Proceeds from issuance of long-term debt	750	1,250
Payments on long-term debt	(696)	(700)
Cash distributions	(2,275)	(1,425)
Other, net	(9)	(19)
Net cash provided by (used for) financing activities	(2,230)	(894)
Increase (decrease) in cash and cash equivalents	164	917
Cash and cash equivalents:
Beginning of period	1,975	3,218
End of period	2,139	4,135
SUPPLEMENTAL CASH FLOW INFORMATION
Interest paid, net of amounts capitalized	532	530
Capital investments accrued but not yet paid	93	103
Income taxes paid, net of refunds	$ 226	$ 212