Pension Benefits - Net Periodic Pension Cost (Details) - Pension Plan - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 26, 2021
Pension Benefits
Service cost	$ 5,742	$ 11,631	$ 9,200
Interest cost	66,011	40,492	34,869
Expected return on plan assets	(76,489)	(55,229)	(50,711)
Amortization and other costs	6,192	19,637	27,500
Amortization of prior service (credit)/cost	(1,895)	(1,897)	(1,890)
Effect of settlement/curtailment	0	0	(163)
Net periodic pension (credit)/cost	(439)	14,634	18,805
Qualified Plans
Pension Benefits
Service cost	5,669	11,526	9,105
Interest cost	56,793	35,350	30,517
Expected return on plan assets	(76,489)	(55,229)	(50,711)
Amortization and other costs	2,654	13,065	20,225
Amortization of prior service (credit)/cost	(1,945)	(1,945)	(1,945)
Effect of settlement/curtailment	0	0	0
Net periodic pension (credit)/cost	(13,318)	2,767	7,191
Non- Qualified Plans
Pension Benefits
Service cost	73	105	95
Interest cost	9,218	5,142	4,352
Expected return on plan assets	0	0	0
Amortization and other costs	3,538	6,572	7,275
Amortization of prior service (credit)/cost	50	48	55
Effect of settlement/curtailment	0	0	(163)
Net periodic pension (credit)/cost	$ 12,879	$ 11,867	$ 11,614