Consolidated Statements of Cash Flows - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
OPERATING ACTIVITIES
Net income	$ 838	$ 784
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	573	520
Deferred income taxes	118	191
Long-term casualty and environmental liabilities, net	(7)	(12)
Other, net	(71)	(62)
Changes in current assets and liabilities:
Accounts receivable, net	28	13
Materials and supplies	(8)	(15)
Other current assets	(8)	(130)
Accounts payable and other current liabilities	145	67
Net cash provided by operating activities	1,608	1,356
INVESTING ACTIVITIES
Capital expenditures excluding equipment	(545)	(676)
Acquisition of equipment	(129)	(204)
Purchases of investments and investments in time deposits	(6)	(1)
Proceeds from sales of investments and maturities of time deposits	4	4
Other, net	(170)	(240)
Net cash used for investing activities	(846)	(1,117)
FINANCING ACTIVITIES
Proceeds from issuance of long-term debt	1,250	0
Payments on long-term debt	(21)	(212)
Cash distributions	(625)	(750)
Other, net	(18)	0
Net cash provided by (used for) financing activities	586	(962)
Increase (decrease) in cash and cash equivalents	1,348	(723)
Cash and cash equivalents:
Beginning of period	3,218	2,329
End of period	4,566	1,606
SUPPLEMENTAL CASH FLOW INFORMATION
Interest paid, net of amounts capitalized	316	301
Capital investments accrued but not yet paid	101	108
Income taxes paid, net of refunds	$ 5	$ 15