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Accounts receivable (Tables)
12 Months Ended
Dec. 31, 2013
Notes To Financial Statements [Abstract]  
Accounts receivable
In millions December 31,20132012
Freight  $675$674
Non-freight    147 167
Gross accounts receivable   822 841
Allowance for doubtful accounts   (7) (10)
Net accounts receivable  $815$831