Schedule Of Valuation And Qualifying Accounts (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Presented in Consolidated Statements of Financial Position [Abstract]
Allowance for doubtful accounts - current	$ 5	$ 1
Allowance for doubtful accounts - long-term	16	22
Accrued casualty costs, current	249	207
Allowance For Doubtful Accounts [Member]
Schedule Of Valuation And Qualifying Accounts [Line Items]
Balance, beginning of period	23	37	50
Reduction to expense		(4)	(1)
Charges to expense	5
Net write-offs / cash payments and other reductions	(7)	(10)	(12)
Balance, end of period	21	23	37
Presented in Consolidated Statements of Financial Position [Abstract]
Allowance for doubtful accounts - current	5	1	4
Allowance for doubtful accounts - long-term	16	22	33
Accrued Casualty Costs [Member]
Schedule Of Valuation And Qualifying Accounts [Line Items]
Balance, beginning of period	702	734	778
Charges to expense	256	188	190
Net write-offs / cash payments and other reductions	(201)	(220)	(234)
Balance, end of period	757	702	734
Presented in Consolidated Statements of Financial Position [Abstract]
Accrued casualty costs, current	249	207	213
Accrued casualty costs, long-term	$ 508	$ 495	$ 521

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Total of allowances and reserves, the valuation and qualifying accounts that are either netted against the cost of an asset (in order to value it at its carrying value) or that reflect a liability established to represent expected future costs, charged to costs and expenses.

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- Definition

A valuation allowance for trade and other receivables due to an Entity within one year (or the normal operating cycle, whichever is longer) that are expected to be uncollectible.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 4

-Article 5

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

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-Topic 210

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A valuation allowance for receivables due to an Entity for more than one year from the balance sheet date that are expected to be uncollectible.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef

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-Name Regulation S-X (SX)

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Amount of loss contingency liability expected to be resolved within one year or the normal operating cycle, if longer.

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Amount of loss contingency liability expected to be resolved after one year or beyond the normal operating cycle, if longer.

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Total of the deductions in a given period to allowances and reserves, the valuation and qualifying accounts that are either netted against the cost of an asset (in order to value it at its carrying value) or that reflect a liability established to represent expected future costs, representing receivables written off as uncollectible and portions of the reserves utilized, respectively.

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