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Nature of Operations and Significant Accounting Policies (Details) (USD $)
In Millions, unless otherwise specified
3 Months Ended 6 Months Ended 12 Months Ended
Jun. 28, 2013
states
mi
Jun. 29, 2012
Jun. 28, 2013
states
mi
Jun. 29, 2012
Dec. 28, 2012
Background          
Total number of rail route miles 21,000   21,000    
Rail network states number 23   23    
Fiscal Year          
Number of weeks in fiscal quarter P13W P13W P13W P13W  
Number of weeks in fiscal year     P52W   P52W
Allowance for Doubtful Accounts          
Allowance for doubtful accounts $ 40   $ 40   $ 36