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Nature of Operations and Significant Accounting Policies - Narrative (Details) mi in Thousands, $ in Millions | 6 Months Ended |
--- | --- | ---
Jun. 26, 2015 USD ($) state mi | Jun. 27, 2014 | Dec. 26, 2014 USD ($)
Background |  |  |
Total number of rail route miles | 21 |  |
Number of states rail network serves | state | 23 |  |
Fiscal Year |  |  |
Number of days in fiscal year | 364 days | 364 days |
Number of days in fiscal quarter | 91 days | 91 days |
Number of days in fiscal quarter YTD | 182 days | 182 days |
Allowance for Doubtful Accounts |  |  |
Allowance for doubtful accounts | $ | $ 37 |  | $ 41

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