Benefit Plans (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 28, 2019	Sep. 29, 2018	Sep. 28, 2019	Sep. 29, 2018
Pension Benefits [Member]
Components of net periodic benefit cost (income) [Abstract]
Service cost	$ 0	$ 22	$ 0	$ 66
Interest cost	1,455	1,478	4,365	4,436
Expected return on plan assets	(2,077)	(2,290)	(6,230)	(6,869)
Amortization of net (gain) loss	485	293	1,455	877
Net periodic benefit income	(137)	(497)	(410)	(1,490)
Other Benefits [Member]
Components of net periodic benefit cost (income) [Abstract]
Service cost	64	59	191	175
Interest cost	153	147	459	441
Amortization of prior service credit	(226)	(226)	(677)	(677)
Amortization of net (gain) loss	(10)	14	(31)	43
Net periodic benefit income	$ (19)	$ (6)	$ (58)	$ (18)