Benefit Plans - Assets of the Plan Measured at Fair Value on a Recurring Basis Using Significant Unobservable Inputs (Details) $ in Thousands	12 Months Ended
	Dec. 26, 2020 USD ($)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Beginning balance	$ 183,486
Ending balance	78,480
Pension Plan [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Beginning balance	183,486
Ending balance	78,480
Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Beginning balance	7,915
Ending balance	6,904
Fair Value, Inputs, Level 3 [Member] | Pension Plan [Member] | Limited Partner [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Beginning balance	7,915
Surplus assets	(1,104)
Net appreciation in fair value	93
Ending balance	$ 6,904