Other Postretirement Benefits - Schedule of Components of Net Periodic Postretirement Benefit Income (Details) - Other Postretirement Benefit Plans - USD ($) $ in Thousands	12 Months Ended
	Dec. 27, 2020	Dec. 29, 2019	Dec. 30, 2018
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	$ 29	$ 27	$ 21
Interest cost	1,026	1,602	1,476
Amortization and other costs	3,051	3,375	4,735
Amortization of prior service credit	(4,225)	(4,766)	(6,157)
Net periodic pension (income)/cost	$ (119)	$ 238	$ 75