Other Postretirement Benefits - Changes in the Benefit Obligation and Plan Assets and Other Amounts (Details) - Other Postretirement Benefit Plans - USD ($) $ in Thousands	12 Months Ended
	Dec. 26, 2021	Dec. 27, 2020	Dec. 29, 2019
Change in benefit obligation
Benefit obligation at beginning of year	$ 43,308	$ 42,803
Service cost	53	29	$ 27
Interest cost	565	1,026	1,602
Plan participants’ contributions	2,319	2,820
Actuarial (gain)/loss	2,254	4,044
Benefits paid	(7,892)	(7,414)
Benefit obligation at end of year	40,607	43,308	$ 42,803
Change in plan assets
Fair value of plan assets at beginning of year	0
Employer contributions	5,573	4,594
Plan participants’ contributions	2,319	2,820
Benefits paid	(7,892)	(7,414)
Fair value of plan assets at end of year	0	0
Amount recognized in the Consolidated Balance Sheets
Current liabilities	(4,521)	(4,618)
Noncurrent liabilities	(36,086)	(38,690)
Net amount recognized	(40,607)	(43,308)
Amount recognized in accumulated other comprehensive loss
Actuarial loss	25,632	26,785
Prior service credit	(368)	(3,466)
Total	$ 25,264	$ 23,319