Other Postretirement Benefits - Schedule of Assumptions Used (Details) - Other Postretirement Benefit Plans	12 Months Ended
	Dec. 27, 2020	Dec. 29, 2019	Dec. 30, 2018
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Benefit Obligation [Abstract]
Discount rate	2.01%	2.94%
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	2.94%	4.18%	3.46%
Discount rate in effect for determining service cost	3.04%	4.19%	3.56%
Discount rate in effect for determining interest cost	2.55%	3.71%	3.01%
Estimated increase in compensation level	3.50%	3.50%	3.50%