Pension Benefits (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 28, 2015	Jun. 29, 2014	Jun. 28, 2015	Jun. 29, 2014
Compensation and Retirement Disclosure [Abstract]
Service cost	$ 297	$ 283	$ 601	$ 565
Interest cost	525	917	1,060	1,833
Expected return on plan assets	(33)	(1)	(67)	(1)
Amortization of actuarial loss	733	386	1,483	771
Amortization of prior service costs	7	3	13	6
Net periodic pension cost	$ 1,529	$ 1,588	3,090	$ 3,174
Estimated employer contributions			4,300
Pension contributions			$ 2,200