Pension Plans - Pension plan net periodic benefit costs (Details) - USD ($) $ in Thousands	3 Months Ended
	Apr. 02, 2021	Apr. 03, 2020
Qualified Pension Plan
Defined Benefit Plan Disclosure
Service cost	$ 1,300	$ 1,309
Interest cost on projected benefit obligation	3,525	5,255
Expected return on plan assets	(11,275)	(10,796)
Amortization of net loss	1,075	1,201
Net pension (income) cost	(5,375)	(3,031)
SERP
Defined Benefit Plan Disclosure
Service cost	0	0
Interest cost on projected benefit obligation	15	41
Expected return on plan assets	0	0
Amortization of net loss	17	236
Net pension (income) cost	$ 32	$ 277