Other Postretirement Benefits - Schedule of Assumptions Used (Details) - Other Postretirement Benefit Plans, Defined Benefit [Member]	12 Months Ended
	Dec. 25, 2016	Dec. 27, 2015	Dec. 28, 2014
Other Postretirement Benefits
Discount rate for determining projected benefit obligation	4.05%	3.74%	4.22%
Discount rate in effect for determining service cost	4.24%	3.74%	4.22%
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Benefit Obligation [Abstract]
Discount rate	3.94%	4.04%
Estimated increase in compensation level used to calculate benefit obligation	3.50%	3.50%
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Net Periodic Benefit Cost [Abstract]
Discount rate used to calculate net periodic benefit cost	2.96%	3.74%	4.22%
Estimated increase in compensation level use to calculate net periodic benefit cost	3.50%	3.50%	3.50%