Consolidated Statements of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
OPERATING ACTIVITIES
Net income	$ 4,248	$ 3,869	$ 3,793
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	2,001	2,123	1,973
Deferred income taxes	1,148	941	583
Long-term casualty and environmental liabilities, net	(35)	(43)	(98)
Contributions to qualified pension plan	0	0	(25)
Other, net	(47)	(310)	(88)
Changes in current assets and liabilities:
Accounts receivable, net	196	(88)	(130)
Materials and supplies	(34)	40	(35)
Other current assets	(4)	(36)	(6)
Accounts payable and other current liabilities	(298)	85	(205)
Net cash provided by operating activities	7,175	6,581	5,762
INVESTING ACTIVITIES
Capital expenditures excluding equipment	(4,425)	(3,734)	(2,975)
Acquisition of equipment	(1,226)	(1,509)	(943)
Purchases of Investments and investments in time deposits	(151)	0	0
Proceeds from sales of investments and maturities of time deposits	27	0	0
Partnership Investment	(36)	0	0
Other, net	(16)	(6)	55
Net cash used for investing activities	(5,827)	(5,249)	(3,863)
FINANCING ACTIVITIES
Proceeds from issuance of long-term debt	3,000	3,000	3,000
Payments on long-term debt	(371)	(641)	(440)
Cash distributions	(4,000)	(3,500)	(4,000)
Other, net	(32)	(32)	(28)
Net cash used for financing activities	(1,403)	(1,173)	(1,468)
Increase/(decrease) in cash and cash equivalents	(55)	159	431
Cash and cash equivalents:
Beginning of period	2,384	2,225	1,794
End of period	2,329	2,384	2,225
SUPPLEMENTAL CASH FLOW INFORMATION
Interest paid, net of amounts capitalized	953	859	772
Capital investments accrued but not yet paid	421	293	224
Income taxes paid, net of refunds	$ 1,281	$ 1,366	$ 1,752