Employee Benefit Plans (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 29, 2013	Jun. 30, 2012	Jun. 29, 2013	Jun. 30, 2012
Components of net periodic benefit costs:
Service cost	$ 532	$ 516	$ 1,064	$ 1,032
Interest cost	2,026	2,201	4,052	4,402
Expected return on plan assets	(1,629)	(1,509)	(3,258)	(3,018)
Amortization of unrecognized net loss	1,157	951	2,314	1,902
Amortization of prior service cost	11	11	22	22
Net periodic benefit costs	$ 2,097	$ 2,170	$ 4,194	$ 4,340