Benefit Plans (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 27, 2021	Mar. 28, 2020
Pension Benefits [Member]
Components of net periodic benefit cost (income) [Abstract]
Interest cost	$ 313	$ 858
Expected return on plan assets	(904)	(1,495)
Amortization of net loss (gain)	378	460
Net periodic benefit income	(213)	(177)
Other Benefits [Member]
Components of net periodic benefit cost (income) [Abstract]
Interest cost	87	109
Amortization of net loss (gain)	(31)	(53)
Service cost	65	61
Amortization of prior service credit	(118)	(226)
Net periodic benefit income	$ 3	$ (109)