Nature of Operations and Significant Accounting Policies - Narrative (Details) mi in Thousands, $ in Millions	1 Months Ended	3 Months Ended
	Mar. 31, 2017 USD ($) state employee mi	Jun. 30, 2017 USD ($)	Dec. 30, 2016 USD ($)
Background
Total number of rail route miles | mi	21
Number of states rail network serves | state	23
Allowance for Doubtful Accounts
Allowance for doubtful accounts	$ 23		$ 33
Management Streamlining Initiative
Other Items [Abstract]
Workforce reduction (number of employees) | employee	765
Severance and Pension | Scenario, Forecast | Management Streamlining Initiative
Other Items [Abstract]
Payments for restructuring		$ 90