Benefit Plans (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jul. 01, 2017	Jul. 02, 2016	Jul. 01, 2017	Jul. 02, 2016
Pension Benefits [Member]
Components of net periodic benefit cost (income) [Abstract]
Service cost	$ 36	$ 165	$ 71	$ 360
Interest cost	1,653	1,969	3,318	3,944
Expected return on plan assets	(2,186)	(2,466)	(4,368)	(4,932)
Amortization of net (gain) loss	516	746	1,072	1,520
Net periodic benefit income	19	414	93	892
Other Benefits [Member]
Components of net periodic benefit cost (income) [Abstract]
Service cost	53	60	109	122
Interest cost	146	149	295	305
Amortization of prior service credit	(226)	(224)	(451)	(448)
Amortization of net (gain) loss	(15)	(20)	(20)	(18)
Net periodic benefit income	$ (42)	$ (35)	$ (67)	$ (39)