Other Postretirement Benefits - Schedule of Assumptions Used (Details) - Other Postretirement Benefit Plans [Member]	12 Months Ended
	Dec. 31, 2017	Dec. 25, 2016	Dec. 27, 2015
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Benefit Obligation [Abstract]
Discount rate	3.46%	3.94%
Rate of increase in compensation levels	3.50%	3.50%
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Net Periodic Benefit Cost [Abstract]
Discount rate for determining projected benefit obligation	3.93%	4.05%	3.74%
Discount rate in effect for determining service cost	4.08%	4.24%	3.74%
Discount rate in effect for determining interest cost	3.21%	2.96%	3.74%
Estimated increase in compensation level	3.50%	3.50%	3.50%