Pension Plans - Pension plan net periodic benefit costs (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jul. 01, 2022	Jun. 30, 2023	Jul. 01, 2022
Qualified Pension Plan
Defined Benefit Plan Disclosure
Service cost	$ (1,441)	$ (882)	$ (2,891)	$ (1,682)
Interest cost on projected benefit obligation	7,342	4,349	14,592	8,599
Expected return on plan assets	(9,597)	(10,564)	(19,147)	(21,089)
Amortization of net loss	1,972	1,154	3,847	2,129
Net pension cost (income)	1,158	(4,179)	2,183	(8,679)
SERP
Defined Benefit Plan Disclosure
Service cost	0	0	0	0
Interest cost on projected benefit obligation	44	22	88	44
Expected return on plan assets	0	0	0	0
Amortization of net loss	0	15	0	30
Net pension cost (income)	$ 44	$ 37	$ 88	$ 74