Employee Benefit Plans (Details) - Components of other postretirement benefit cost (Other Postretirement Benefit Plan [Member], USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 28, 2014	Jun. 29, 2013	Jun. 28, 2014	Jun. 29, 2013
Other Postretirement Benefit Plan [Member]
Employee Benefit Plans (Details) - Components of other postretirement benefit cost [Line Items]
Interest cost	$ 28	$ 25	$ 55	$ 50
Amortization of prior service benefit	(38)	(42)	(76)	(84)
Amortization of accumulated loss	4	8	7	17
Net periodic postretirement benefit income	$ (6)	$ (9)	$ (14)	$ (17)