Employee Benefit Plans (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 28, 2014	Jun. 29, 2013	Jun. 28, 2014	Jun. 29, 2013
Components of net periodic benefit costs:
Service cost	$ 333	$ 532	$ 666	$ 1,064
Interest cost	2,205	1,967	4,410	3,934
Expected return on plan assets	(1,756)	(1,629)	(3,512)	(3,258)
Amortization of net loss	821	1,147	1,642	2,294
Amortization of prior service cost	11	11	22	22
Net periodic benefit costs	$ 1,614	$ 2,028	$ 3,228	$ 4,056