Pension Benefits - Net Periodic Pension Cost (Details) - USD ($) $ in Thousands	1 Months Ended	12 Months Ended
	Oct. 31, 2020	Dec. 26, 2021	Dec. 27, 2020	Dec. 29, 2019
Pension Benefits
Benefit obligation	$ 236,300
Pension settlement expense	$ 80,600
Pension Plan
Pension Benefits
Service cost		$ 9,200	$ 10,548	$ 5,231
Interest cost		34,869	50,311	67,255
Expected return on plan assets		(50,711)	(67,146)	(80,877)
Amortization and other costs		27,500	27,959	23,020
Amortization of prior service (credit)/cost		(1,890)	(1,894)	(1,932)
Effect of settlement/curtailment		(163)	80,079	(373)
Net periodic pension cost/(income)		18,805	99,857	12,324
Benefit obligation		1,714,954	1,808,605	1,908,035
Qualified Plan | Pension Plan
Pension Benefits
Service cost		9,105	10,429	5,113
Interest cost		30,517	43,710	58,835
Expected return on plan assets		(50,711)	(67,146)	(80,877)
Amortization and other costs		20,225	21,887	18,639
Amortization of prior service (credit)/cost		(1,945)	(1,945)	(1,945)
Effect of settlement/curtailment		0	80,641	0
Net periodic pension cost/(income)		7,191	87,576	(235)
Benefit obligation		1,475,764	1,549,012	1,660,287
Nonqualified Plan | Pension Plan
Pension Benefits
Service cost		95	119	118
Interest cost		4,352	6,601	8,420
Expected return on plan assets		0	0	0
Amortization and other costs		7,275	6,072	4,381
Amortization of prior service (credit)/cost		55	51	13
Effect of settlement/curtailment		(163)	(562)	(373)
Net periodic pension cost/(income)		11,614	12,281	12,559
Benefit obligation		$ 239,190	$ 259,593	$ 247,748