Nature of Operations and Significant Accounting Policies - Narrative (Details) mi in Thousands, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 25, 2015 USD ($) state mi	Sep. 26, 2014	Sep. 25, 2015 USD ($) state mi	Sep. 26, 2014	Dec. 26, 2014 USD ($)
Background
Total number of rail route miles	21		21
Number of states rail network serves | state	23		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			273 days	273 days
Allowance for Doubtful Accounts
Allowance for doubtful accounts | $	$ 39		$ 39		$ 41