Employee Benefit Plans (Details) - Components of other postretirement benefit cost - Other Postretirement Benefit Plan [Member] - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 27, 2015	Jun. 28, 2014	Jun. 27, 2015	Jun. 28, 2014
Employee Benefit Plans (Details) - Components of other postretirement benefit cost [Line Items]
Interest cost	$ 70	$ 74	$ 140	$ 149
Amortization of prior service benefit	(23)	(39)	(46)	(77)
Amortization of actuarial loss	28	20	58	38
Net periodic postretirement benefit cost	$ 75	$ 55	$ 152	$ 110