Employee Benefit Plans (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 30, 2013	Mar. 31, 2012
Components of net periodic benefit costs:
Service cost	$ 532	$ 516
Interest cost	2,026	2,201
Expected return on plan assets	(1,629)	(1,509)
Amortization of unrecognized net loss	1,157	951
Amortization of prior service cost	11	11
Net periodic benefit costs	$ 2,097	$ 2,170