Consolidated Balance Sheets (USD $) In Millions, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Current assets:
Cash and cash equivalents	$ 2,385	$ 1,794
Accounts receivable, net	1,249	1,168
Materials and supplies	839	800
Current portion of deferred income taxes	207	341
Other current assets	159	77
Total current assets	4,839	4,180
Property and equipment, net of accumulated depreciation of $1,720 and $1,626, respectively	50,396	50,070
Goodwill	14,836	14,836
Intangible assets, net	1,038	1,114
Other assets	1,857	1,816
Total assets	72,966	72,016
Current liabilities:
Accounts payable and other current liabilities	2,916	3,122
Long-term debt due within one year	923	453
Total current liabilities	3,839	3,575
Deferred income taxes	16,334	16,319
Long-term debt	15,028	14,080
Intangible liabilities, net	1,151	1,214
Pension and retiree health and welfare liability	755	786
Casualty and environmental liabilities	738	750
Other liabilities	993	963
Total liabilities	38,838	37,687
Commitments and contingencies (see Notes 6 and 7)
Equity:
Member's Equity	34,372	34,574
Accumulated other comprehensive loss	(244)	(245)
Total equity	34,128	34,329
Total liabilities and equity	$ 72,966	$ 72,016