Pension Plans - Pension plan net periodic benefit costs (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Oct. 01, 2021	Oct. 02, 2020	Oct. 01, 2021	Oct. 02, 2020
Qualified Pension Plan
Defined Benefit Plan Disclosure
Service cost	$ 325	$ 1,309	$ 976	$ 3,927
Interest cost on projected benefit obligation	3,541	5,255	10,624	15,765
Expected return on plan assets	(11,294)	(10,796)	(33,883)	(32,388)
Amortization of net loss	1,111	1,201	3,333	3,603
Net pension (income) cost	(6,317)	(3,031)	(18,950)	(9,093)
SERP
Defined Benefit Plan Disclosure
Service cost	0	0	0	0
Interest cost on projected benefit obligation	16	41	45	124
Expected return on plan assets	0	0	0	0
Amortization of net loss	14	236	49	708
Net pension (income) cost	$ 30	$ 277	$ 94	$ 832