Employee Benefit Plans - Components Of Net Periodic Benefit Costs (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 26, 2022	Jun. 27, 2021	Jun. 26, 2022	Jun. 27, 2021
Pension and SERPA Benefits:
Defined Benefit Plan Disclosure
Service cost	$ 4,763	$ 6,348	$ 9,525	$ 12,696
Interest cost	15,472	15,472	30,945	30,942
Expected return on plan assets	(31,476)	(32,720)	(62,952)	(65,440)
Amortization of unrecognized: Prior service credit	(328)	(312)	(656)	(624)
Amortization of unrecognized: Net loss	7,978	18,386	15,956	36,772
Settlement (gain) loss	0	0	(256)	816
Net periodic benefit (income) cost	(3,591)	7,174	(7,438)	15,162
Postretirement Healthcare Benefits:
Defined Benefit Plan Disclosure
Service cost	1,161	1,288	2,322	2,576
Interest cost	1,904	1,626	3,808	3,252
Expected return on plan assets	(3,809)	(3,495)	(7,618)	(6,990)
Amortization of unrecognized: Prior service credit	(581)	(581)	(1,162)	(1,162)
Amortization of unrecognized: Net loss	122	264	244	528
Net periodic benefit (income) cost	$ (1,203)	$ (898)	$ (2,406)	$ (1,796)