Benefit Plans (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 29, 2019	Jun. 30, 2018	Jun. 29, 2019	Jun. 30, 2018
Pension Benefits [Member]
Components of net periodic benefit cost (income) [Abstract]
Service cost	$ 0	$ 20	$ 0	$ 44
Interest cost	1,443	1,465	2,910	2,958
Expected return on plan assets	(2,077)	(2,290)	(4,153)	(4,579)
Amortization of net (gain) loss	440	235	970	584
Net periodic benefit income	(194)	(570)	(273)	(993)
Other Benefits [Member]
Components of net periodic benefit cost (income) [Abstract]
Service cost	63	56	127	116
Interest cost	153	146	306	294
Amortization of prior service credit	(225)	(225)	(451)	(451)
Amortization of net (gain) loss	(13)	11	(21)	29
Net periodic benefit income	$ (22)	$ (12)	$ (39)	$ (12)