Benefit Plans (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Oct. 01, 2016	Sep. 26, 2015	Oct. 01, 2016	Sep. 26, 2015
Pension Benefits [Member]
Components of net periodic benefit cost (income) [Abstract]
Service cost	$ 180	$ 250	$ 540	$ 750
Interest cost	1,973	2,041	5,917	6,122
Expected return on plan assets	(2,466)	(2,654)	(7,398)	(7,963)
Amortization of net (gain) loss	760	685	2,280	2,055
Net periodic benefit (income) cost	447	322	1,339	964
Other Benefits [Member]
Components of net periodic benefit cost (income) [Abstract]
Service cost	61	90	183	270
Interest cost	153	193	458	579
Amortization of prior service (credit) cost	(224)	2	(672)	5
Amortization of net (gain) loss	(9)	(7)	(27)	(20)
Net periodic benefit (income) cost	$ (19)	$ 278	$ (58)	$ 834