Pension and Other Postretirement Benefits - Pension Benefits - Net Periodic Pension Cost (Details) - Pension Plan - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 26, 2022	Jun. 27, 2021	Jun. 26, 2022	Jun. 27, 2021
Pension Benefits
Service cost	$ 2,882	$ 2,276	$ 5,763	$ 4,552
Interest cost	10,121	8,717	20,243	17,434
Expected return on plan assets	(13,807)	(12,678)	(27,615)	(25,355)
Amortization of actuarial loss	4,909	6,879	9,819	13,755
Amortization of prior service credit	(486)	(486)	(972)	(972)
Net periodic postretirement benefit cost	3,619	4,708	7,238	9,414
Qualified Plans
Pension Benefits
Service cost	2,882	2,276	5,763	4,552
Interest cost	8,837	7,629	17,675	15,258
Expected return on plan assets	(13,807)	(12,678)	(27,615)	(25,355)
Amortization of actuarial loss	3,266	5,057	6,532	10,113
Amortization of prior service credit	(486)	(486)	(972)	(972)
Net periodic postretirement benefit cost	692	1,798	1,383	3,596
Pension contributions			5,100	4,200
Expected future employer contributions	10,000		10,000
Non- Qualified Plans
Pension Benefits
Service cost	0	0	0	0
Interest cost	1,284	1,088	2,568	2,176
Expected return on plan assets	0	0	0	0
Amortization of actuarial loss	1,643	1,822	3,287	3,642
Amortization of prior service credit	0	0	0	0
Net periodic postretirement benefit cost	$ 2,927	$ 2,910	$ 5,855	$ 5,818