Employee Benefit Plans - Components of Net Periodic Benefit Cost (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jul. 04, 2021	Jun. 28, 2020	Jul. 04, 2021	Jun. 28, 2020
Retirement Plans
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 1,020	$ 1,003	$ 1,981	$ 2,085
Interest cost	9,657	12,549	19,764	25,230
Expected return on plan assets	(8,650)	(12,227)	(18,311)	(24,807)
Amortization of prior service cost	235	247	461	497
Amortization of net actuarial loss	6,378	7,258	13,249	14,134
Effect of curtailment loss	0	31	0	31
Effect of settlement loss	547,631	38	547,631	661
Net periodic benefit cost	556,271	8,899	564,775	17,831
Retiree Health and Life Insurance Plans
Defined Benefit Plan Disclosure [Line Items]
Service cost	95	93	189	176
Interest cost	50	81	100	165
Expected return on plan assets	(111)	(93)	(224)	(183)
Amortization of prior service cost	0	(69)	0	(137)
Amortization of net actuarial loss	(181)	(215)	(377)	(412)
Net periodic benefit cost	$ (147)	$ (203)	$ (312)	$ (391)