Consolidated Statements of Cash Flows - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
OPERATING ACTIVITIES
Net income	$ 1,145	$ 838
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	571	573
Deferred income taxes	102	118
Long-term casualty and environmental liabilities, net	(5)	(7)
Other, net	(90)	(71)
Changes in current assets and liabilities:
Accounts receivable, net	5	28
Materials and supplies	(4)	(8)
Other current assets	(91)	(8)
Accounts payable and other current liabilities	(13)	145
Net cash provided by operating activities	1,620	1,608
INVESTING ACTIVITIES
Capital expenditures excluding equipment	(519)	(545)
Acquisition of equipment	(46)	(129)
Purchases of investments and investments in time deposits	(8)	(6)
Proceeds from sales of investments and maturities of time deposits	7	4
Other, net	(94)	(170)
Net cash used for investing activities	(660)	(846)
FINANCING ACTIVITIES
Proceeds from issuance of long-term debt	750	1,250
Payments on long-term debt	(671)	(21)
Cash distributions	(1,100)	(625)
Other, net	(8)	(18)
Net cash provided by (used for) financing activities	(1,029)	586
Increase (decrease) in cash and cash equivalents	(69)	1,348
Cash and cash equivalents:
Beginning of period	1,975	3,218
End of period	1,906	4,566
SUPPLEMENTAL CASH FLOW INFORMATION
Interest paid, net of amounts capitalized	310	316
Capital investments accrued but not yet paid	86	101
Income taxes paid, net of refunds	$ 7	$ 5