Employee Benefit Plans (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jul. 02, 2011	Jun. 30, 2012	Jul. 02, 2011
Components of net periodic benefit costs:
Service cost	$ 516	$ 381	$ 1,032	$ 762
Interest cost	2,201	2,274	4,402	4,548
Expected return on plan assets	(1,509)	(1,656)	(3,018)	(3,312)
Amortization of unrecognized net loss	951	858	1,902	1,716
Amortization of prior service cost	11	11	22	22
Net periodic benefit costs	$ 2,170	$ 1,868	$ 4,340	$ 3,736