Employee Benefit Plans - Components Of Net Periodic Benefit Costs (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 27, 2022	Mar. 28, 2021
Pension and SERPA Benefits:
Defined Benefit Plan Disclosure
Service cost	$ 4,763	$ 6,348
Interest cost	15,472	15,470
Expected return on plan assets	(31,476)	(32,720)
Amortization of unrecognized: Prior service credit	(328)	(312)
Amortization of unrecognized: Net loss	7,978	18,386
Settlement (gain) loss	(256)	816
Net periodic benefit (income) cost	(3,847)	7,988
Postretirement Healthcare Benefits:
Defined Benefit Plan Disclosure
Service cost	1,161	1,288
Interest cost	1,904	1,626
Expected return on plan assets	(3,809)	(3,495)
Amortization of unrecognized: Prior service credit	(581)	(581)
Amortization of unrecognized: Net loss	122	264
Net periodic benefit (income) cost	$ (1,203)	$ (898)