Other Postretirement Benefits (Details) - Other Postretirement Benefit Plan - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 28, 2015	Jun. 29, 2014	Jun. 28, 2015	Jun. 29, 2014
Pension Benefits
Service cost	$ 147	$ 147	$ 294	$ 294
Interest cost	689	1,010	1,377	2,020
Amortization of actuarial loss	1,303	1,184	2,606	2,368
Amortization of prior service credit	(2,475)	(1,600)	(4,950)	(3,200)
Net periodic pension cost/postretirement benefit expense	$ (336)	$ 741	$ (673)	$ 1,482