Consolidated Statements of Cash Flows - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
OPERATING ACTIVITIES
Net income	$ 784	$ 1,045
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	520	496
Deferred income taxes	191	143
Long-term casualty and environmental liabilities, net	(12)	(11)
Other, net	(62)	(63)
Changes in current assets and liabilities:
Accounts receivable, net	13	49
Materials and supplies	(15)	(25)
Other current assets	(130)	(82)
Accounts payable and other current liabilities	67	178
Net cash provided by operating activities	1,356	1,730
INVESTING ACTIVITIES
Capital expenditures excluding equipment	(676)	(844)
Acquisition of equipment	(204)	(347)
Purchases of investments and investments in time deposits	(1)	(45)
Proceeds from sales of investments and maturities of time deposits	4	0
Other, net	(240)	(64)
Net cash used for investing activities	(1,117)	(1,300)
FINANCING ACTIVITIES
Proceeds from issuance of long-term debt	0	1,500
Payments on long-term debt	(212)	(283)
Cash distributions	(750)	(1,000)
Other, net	0	(16)
Net cash (used for) provided by financing activities	(962)	201
(Decrease) increase in cash and cash equivalents	(723)	631
Cash and cash equivalents:
Beginning of period	2,329	2,384
End of period	1,606	3,015
SUPPLEMENTAL CASH FLOW INFORMATION
Interest paid, net of amounts capitalized	301	285
Capital investments accrued but not yet paid	108	166
Income taxes paid, net of refunds	$ 15	$ 11